Arthroscopy of the stifle joint is indicated when there is hind leg lameness in the presence of stifle pain, crepitus, swelling, or thickening, with or without drawer instability; or when there are abnormal radiographic findings. The most common condition of the stifle joint is injury to the cranial cruciate ligament, and arthroscopy is ideally suited for diagnosing and managing cruciate ligament injuries. Arthroscopy has greatly increased our knowledge of cranial cruciate ligament disease and has enhanced our ability to diagnose this condition, especially in our ability to make early diagnoses. Increased intra‐articular fluid density in the cranial joint space of the stifle on a lateral radiograph (Figure 7.1), even in the absence of any physical findings, is sufficient indication for stifle joint arthroscopy and a very high percentage of these cases have partial tears of the cranial cruciate ligament. Another radiographic abnormality strongly correlated to cruciate ligament disease are clusters of focal radio‐lucent areas in the inter‐condyloid fossa on anterior–posterior views of the stifle (Figure 7.2). These focal areas of radio‐lucency are also occasionally seen in the area of insertion of the cranial cruciate ligament in the proximal tibia on lateral radiographs (Figure 7.3). The correlation of these radiographic abnormalities with early cranial cruciate ligament injuries was made by performing arthroscopy on dogs with hind leg lameness physical findings that did not support a diagnosis of cranial cruciate ligament injury. If drawer instability is present, it is diagnostically significant, but the absence of drawer instability is not sufficient to rule out cranial cruciate ligament injury as many dogs with hind leg lameness without drawer instability have early partial tears of the cranial cruciate ligament. Cruciate ligament disease is a chronic insidious process, and true acute cranial cruciate ligament injuries are unusual. The vast majority of “acute” presentations have changes on physical examination, in radiographs, and that are seen with arthroscopy to indicate chronicity of months or years duration. Cranial cruciate ligament injuries are also being recognized more and more commonly as a bilateral condition and assessment of the contralateral stifle is indicated when dogs are undergoing evaluation, arthroscopy, and surgery for the symptomatic stifle (Fuller et al. 2014). A minimum of a lateral radiograph of the contralateral stifle is indicated. Meniscal injuries are commonly seen with cranial cruciate ligament ruptures (Ertelt and Fehr 2009; Fehr et al. 1996; Gleason et al. 2020; Kaufman et al. 2017; Mccready and Ness 2016a, b; Neal et al. 2015; Plesman et al. 2013; Pozzi et al. 2008; Ralphs and Whitney 2002; Ritzo et al. 2014; Wustefeld‐Janssens et al. 2016) but are very rare in the presence of normal cruciate ligaments (Adams et al. 2018; Ridge 2006). The authors personal experience with one case of what was diagnosed at the time as an isolated meniscal injury is now, with additional experience, thought to be in error and an early partial cranial cruciate ligament was missed. Damage to the caudal pole of the medial meniscus is the classic concept of meniscal damage with bucket handle tears, parrot beak tears, cranial folding with entrapment, and crushing commonly described. Arthroscopy has revealed multiple types of injuries encompassing all classifications of meniscal damage and involving both the medial and lateral meniscuses. Lateral meniscal injury has been found to be more common than medial meniscal damage. Fraying of the axial margin of the cranial third of the lateral meniscus is the most frequent finding but bucket handle tears, parrot beak tears, and crushing are also seen. Injuries to other soft tissue structures in the stifle joint are uncommon, especially when compared to cranial cruciate ligament injuries. Injuries to the caudal cruciate ligament are uncommon and are difficult to differentiate from cranial cruciate ligament injuries without arthroscopy. The frequency of caudal cruciate ligament injury diagnosis is also decreasing with improved arthroscopic technique allowing earlier diagnosis of minimally damaged cranial cruciate ligaments and the recognition of variations in normal surface appearance of the caudal cruciate ligament. Long digital tendon ruptures or avulsions are seen as a source of lameness originating from the stifle joint but are uncommon. Popliteal tendon avulsions have also been diagnosed as a source of hind leg lameness but are rare. Figure 7.1 A lateral radiographic projection of the stifle joint with increased intra‐articular fluid density in the cranial joint space indicative of a cranial cruciate ligament injury. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.2 An anterior–posterior radiographic projection of a stifle showing focal radio‐lucencies in the inter‐condyloid fossa indicative of cranial cruciate ligament injury. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.3 A lateral radiographic projection of a stifle joint showing a focal radio‐lucency in the proximal tibial tuberosity indicative of cranial cruciate ligament injury. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Specific radiographic changes allowing diagnosis of OCD, patellar luxation, patellar fractures, intra‐articular fractures of the distal femur or proximal tibia, and periarticular or intra‐articular neoplasia can provide a diagnosis before arthroscopy. Radiographic changes indicating degenerative joint disease are nonspecific but are more commonly associated with cranial cruciate ligament injuries than with any other diagnosis. A definitive diagnosis based on radiographs is not possible or necessary, but these changes are an indication for arthroscopy. Preoperative CT or MRI may be beneficial in some cases but do not provide as much information as can be achieved with arthroscopy. Cranial cruciate ligament injuries are the most misdiagnosed and underdiagnosed disease seen in referred patients in the authors’ experience. Diagnosis of earlier more subtle cruciate ligament injuries has become possible using arthroscopy (Ashour et al. 2019; Bleedorn et al. 2011; Fuller et al. 2014). It is not just that arthroscopy allows diagnosis of cruciate ligament injuries before they can be diagnosed with any other technique, but clients are more willing to allow arthroscopy to confirm a diagnosis than they are to allow open surgery. Earlier joint examination achieved before chronic changes can be seen with less sophisticated techniques provides an opportunity to achieve better results. Application of the information gained through arthroscopy to reevaluation of history, physical findings, and radiographs has improved interpretation of findings allowing suspicion of cruciate ligament injuries with more subtle changes. The most important conclusion from this process is that increased intra‐articular fluid density or displacement of the fat pad on a lateral radiograph of the stifle is the earliest consistent indication of cruciate ligament injury with greater than 90% correlation (Figure 7.1). This is consistently seen before bony changes on radiographs, before palpable joint thickening, before medial buttress formation, before detectable drawer instability, and even when there is no pain response to joint manipulation. Stifle arthroscopy was initially used as a diagnostic tool (Kivumbi and Bennett 1981; Siemering 1978; Van Gestel 1985) but currently is the mainstay of stifle surgery with the intra‐articular portion of cruciate ligament surgeries being performed with arthroscopy. The remnants of completely ruptured cranial cruciate ligaments are removed, and the damaged portion of partial tears is debrided with arthroscopy. Any meniscal injuries are addressed with partial meniscectomy under arthroscopic guidance. After completion of arthroscopic management of intra‐articular structures, a TPLO is performed as an open procedure without arthrotomy and with open exposure limited to the proximal tibia. This approach improves intra‐articular assessment of the joint, improves joint debridement, decreases postoperative pain, and shortens recovery times (Hoelzler et al. 2004; Plesman et al. 2013; Pozzi et al. 2008; Ritzo et al. 2014). Arthroscopic stifle debridement has also been performed as the sole treatment for complete cruciate ligament ruptures. The remnants of the cranial cruciate ligament are removed, the caudal attachment of the medial meniscus is released, and the joint is left unstable. This approach has only been applied with complete ruptures of the cranial cruciate ligament in geriatric patients where recovery from a TPLO is a major portion of their remaining life expectancy. Pain is typically reduced dramatically, and recovery times are days to weeks rather than months. This approach was attempted in younger dogs when owners could not or would not enforce the postoperative activity restriction required for a TPLO or other cruciate repair procedures. Short‐term results of this approach in young dogs were good, but long‐term results were poor with extensive degenerative changes and poor limb function requiring surgical stabilization of the joint at a later time. Arthroscopy is also used to release the medial meniscus by transection of the caudal tibial ligament of the medial meniscus. There is extensive disagreement on the benefits vs detriments of medial meniscal release. There is not adequate science to answer the question to release or to not release. It is agreed that releasing the medial meniscus changes the mechanics of the stifle joint. That is not the question. The question is, does releasing the medial meniscus produce better or worse long‐term results than when the meniscus is not released. Any and all of the surgical procedures that are done for cruciate ligament ruptures change the mechanics of the stifle joint. The effects of changes in the mechanics of the stifle joint from the various surgical procedures have not been appropriately studied to be able to differentiate postoperative degenerative changes caused by meniscal release versus those present prior to surgery and those caused by the surgical correction. Extensive degenerative changes are commonly present at the time of diagnoses of most cruciate ligament injuries, and it is unreasonable to expect that the damage will disappear or significantly improve following surgery. Degenerative changes will still be present and may progress. Attributing degenerative changes to meniscal release is not scientifically based. Case selection is a critical factor in the argument about meniscal release. There is no scientific information available to use for case selection. A criterium that the author has used for this decision has been simple. If there is sufficient instability of the joint that access to the caudal meniscotibial ligament of the medial meniscus is easy and can be achieved without the aid of a stifle distractor then the meniscus is released. The meniscus is released by transection of the caudal meniscotibial ligament of the medial meniscus. If there is sufficient damage to the caudal pole of the meniscus requiring a partial meniscectomy, the ligament is cut as part of the meniscectomy. If there is not sufficient instability to allow easy access to the caudal meniscotibial ligament of the medial meniscus then the meniscus is not released. The other factor needed to achieve the best possible long‐term results with cruciate ligament injuries is early intervention. It is ideal to perform corrective surgery before there are any degenerative changes in the joint. Since most cruciate ligament injuries have historically been diagnosed based on the classic physical examination findings of joint pain, joint swelling or thickening, medial buttress formation, and joint instability they are chronic at the time of diagnosis. If we change the approach and pursue all hind leg lameness in dogs as a cruciate ligament injury until proven otherwise and use the information gained from arthroscopy, we can achieve early diagnoses with the potential of improved long‐term results. Stifle arthroscopy has almost exclusively been performed in dogs, but it has also been used in cats for diagnosis and management of cranial cruciate ligament injuries (Mindner et al. 2016; Ruthrauff et al. 2011), OCD (Bright 2010), and patellar fractures (Cusack and Johnson 2013). Since cranial cruciate ligament injuries are the most common finding in the stifle joint, the patient is typically positioned with the leg suspended, prepared, and draped for the surgeon’s preferred cruciate ligament procedure. If there is a specific preoperative diagnosis other than cruciate ligament disease, then this protocol does not need to be followed but is still based on the intended surgery. For unilateral stifle arthroscopy, the patient is placed in either lateral or dorsal recumbency although dorsal recumbency is preferred with the leg extended caudally as this provides more flexibility for manipulations needed to perform a complete arthroscopic examination of the stifle. If the patient is placed in dorsal recumbency, the monitor is placed at the head of the table, the surgeon stands at the foot of the table at the distal end of the limb, and the assistant stands lateral to the joint being evaluated (Figure 2.9). Alternatively, the monitor can be placed on either side of the table facing caudally and far enough cranially to be out of the way of the aseptic field. If the patient is placed in lateral recumbency, the monitor is placed dorsal to the patient, the surgeon stands ventral to the patient at the distal end of the leg being evaluated, and the assistant stands at the foot of the table (Figure 2.10). Stifle arthroscopy is most commonly performed as a unilateral procedure, but bilateral stifle arthroscopy is also performed and is indicated for bilateral OCD and for bilateral complete cranial cruciate ligament ruptures when bilateral corrective procedures are planned at the same surgery. Bilateral stifle arthroscopy is performed with the patient in dorsal recumbency with the monitor, surgeon, and assistant positioned as for unilateral stifle arthroscopy with the patient in dorsal recumbency (Figure 2.9). Bilateral stifle arthroscopy procedures are well tolerated by the patient. The standard telescope portal for the stifle joint is on the cranial aspect of the joint either medial or lateral to the patellar tendon and can be placed anywhere between the distal end of the patella and the tibial plateau. The most common portal position for diagnostic joint examination and for operative procedures involving the cranial cruciate ligament, menisci, and femoral OCD lesions is with the telescope portal medial to the patellar tendon and halfway between the distal end of the patella and the tibial crest (Figure 7.4). This puts the portal at the top of the fat pad and greatly facilitates entry into and examination of the joint. Another commonly used telescope portal is placed lateral to the insertion of the patellar tendon just above the tibial plateau between the patellar tendon and “Gerdy’s tubercle. This location is reported to provide superior visualization of the meniscuses and facilitate operative procedures. The disadvantage of this portal site is that the telescope is placed into the fat pad. A telescope portal can also be placed immediately distal to the patella. This site keeps the telescope away from the fat pad and facilitates examination of the cranial compartment of the joint including the insertions of the cruciate ligaments but access to the menisci is limited. To place the telescope portal, a 20 gauge 1.5” hypodermic needle is placed into the joint at the operative portal site and joint fluid is aspirated (Figure 2.11), the joint is distended with saline (Figure 2.12), a stab incision is made into the joint with a no. 11 scalpel blade at the telescope portal site, and the telescope cannula with the blunt obturator is inserted into the joint (Figure 2.13) directed caudally initially and then is directed proximally into the lateral aspect of the suprapatellar pouch (Figure 7.5). The telescope portal can also be placed lateral to the patellar tendon with the operative portal medial to the tendon. Figure 7.4 Portal sites on the cranial aspect of the stifle joint. The three portals shown are the craniomedial telescope portal (asterisk), the craniolateral operative portal (square), and the suprapatellar egress portal (X). The telescope portal is placed halfway between the distal end of the patella and the proximal end of the tibial crest just medial to the patellar tendon. The operative portal is placed at the same level as the telescope portal and just lateral to the patellar tendon. The egress portal is placed in the suprapatellar pouch of the joint. Source: Modified from Freeman (1999) © John Wiley & Sons. The operative portal is placed on the side of the patellar tendon not used for the telescope portal and typically is placed at the same level as the telescope portal (Figure 7.4). The technique for placing an operative portal using a needle seen inside the joint is not used for the stifle joint, because the fat pad and the extensive villus synovial proliferation occurring with cruciate ligament injuries obscures visualization. Operative portal location in the stifle joint is determined with sufficient accuracy by external landmarks so this technique is not needed. To place the operative portal, a stab incision is made into the joint at the portal site with a no. 11 scalpel blade. A curved mosquito hemostat or the initial operative instrument is worked into the joint with blunt dissection until it is visualized with the telescope. An egress cannula is routinely used for both diagnostic and operative stifle arthroscopy. Minor diagnostic procedures can be performed without an egress cannula but with the extent of villus synovial reaction seen with cruciate ligament injuries, and the need for its removal to allow adequate joint examination, effective egress is required. The suprapatellar pouch is the most practical site for an egress portal in stifle joint arthroscopy (Figure 7.4). This location is out of the way of diagnostic examination or operative procedures and is easier to maintain a cannula at this site. The egress cannula is placed using the telescope cannula at the time of its initial insertion typically before placement of the telescope. Once in the joint the tip of the telescope cannula is positioned into the lateral aspect of the suprapatellar pouch, and the blunt obturator is removed (Figure 7.5). The blunt obturator is replaced with the sharp trocar, and the sharp trocar with the cannula is pushed out through the joint capsule and skin (Figure 7.6). The sharp trocar is removed, and the egress cannula is inserted into the tip of the telescope cannula (Figure 7.7). The telescope cannula is retracted back into the joint with the egress cannula (Figure 7.8). Once the tip of the egress cannula is inside the joint, it is backed out of the telescope cannula until the two cannulas are separated. The egress cannula is positioned in the lateral joint space, its position is confirmed visually in both normal (Figure 7.9) and abnormal joints (Figure 7.10), and it is inserted as far as possible. This is a fast, easy, and trouble‐free method of egress cannula placement. Figure 7.5 Once the telescope cannula is in the joint, with the blunt obturator in place, it is positioned with its tip in the lateral aspect of the suprapatellar pouch. The blunt obturator is removed and replaced with the sharp trocar to allow placement of an egress cannula. Source: Modified from Freeman (1999) © John Wiley & Sons. Figure 7.6 The sharp trocar is inserted into the telescope cannula and locked in place. The sharp trocar and cannula are pushed in a proximal direction out through the joint capsule, subcutaneous tissue, and skin. Source: Modified from Freeman (1999) © John Wiley & Sons. Figure 7.7 The sharp trocar is removed, and the egress cannula is inserted into the tip of the telescope cannula. Source: Modified from Freeman (1999) © John Wiley & Sons. Figure 7.8 The tip of the telescope cannula is retracted back into the joint with the egress cannula. Inside the joint, the egress cannula is backed out of the telescope cannula until they are separated. The egress cannula is then positioned in the lateral joint space. Source: Modified from Freeman (1999) © John Wiley & Sons. Figure 7.9 An egress cannula positioned in the lateral joint space in a normal left stifle joint without villus synovitis. The telescope is looking proximally and laterally from a craniomedial portal into the lateral joint space to visualize the egress cannula in position. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.10 A more typical appearance of an egress cannula in the lateral joint space obscured by villus synovitis secondary to a ruptured right cranial cruciate ligament. The egress cannula is partially visible in the lateral joint compartment with the telescope looking proximally and laterally from a craniomedial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. A similar technique for egress cannula placement is used if the egress cannula is too large to fit within the telescope cannula. This technique uses a changing rod or a switching stick. The tip of the telescope cannula is positioned in the lateral aspect of the suprapatellar pouch and is pushed out through the skin with the sharp trocar as previously described. The sharp trocar is removed, a switching stick is placed into the distal end of the telescope cannula so that it protrudes through the cannulas proximal end, an egress cannula is placed over the switching stick, and the telescope cannula is retracted back into the joint with the switching stick and egress cannula, and the switching stick is removed freeing the egress cannula in the joint. The egress cannula is positioned in the lateral joint space and is inserted as far as possible. This is also a fast, easy, and trouble‐free method of egress cannula placement. There are no significant nerves at risk with placement of the current craniomedial, craniolateral, and suprapatellar stifle joint portals (Figure 7.4) as all nerves are caudal to the joint. The stifle joint is the most difficult of all the joints to examine effectively. This difficulty is due to the stifle’s complex anatomy, the presence of the fat pad in the cranial compartment of the joint, and because of the extensive villus synovial reaction that occurs with cranial cruciate ligament injuries. Stifle joint examination is facilitated by using a consistent systematic approach to visualizing the joint, having adequate fluid pressure and flow, and by using a combination of radio‐frequency and a power shaver to remove part of the fat pad and villus synovial tissue to establish an adequate visual field. Examination of the stifle is begun with the tip of the telescope in the suprapatellar pouch. Fluid egress is momentarily arrested to distend the joint for orientation and to improve the visual field. The telescope is retracted distally until the suprapatellar joint space can be seen with identification of the joint capsule (Figure 7.11). If the image is obscured by cloudy joint fluid, the egress port is opened allowing the fluid to drain and then closed to distend the joint. This procedure is repeated until a clear image is achieved. A plica, or horizontal band of tissue, is commonly present in the suprapatellar pouch as a single‐centered band seen with the joint fully distended and the caudal surface of the quadriceps tendon visible at the top of the image (Figure 7.12), as a single band adjacent to the quadriceps tendon seen with the stifle joint partially distended (Figure 7.13), or as multiple bands (Figure 7.14). As the telescope is retracted further the caudal articular surface of the proximal end of the patella and the proximal articular surface of the trochlear groove come into view (Figure 7.15). The structures seen in the previous figures are used for orientation. During the orientation process, the suprapatellar pouch is examined. Variable accumulations of fat are commonly seen in the suprapatellar pouch (Figure 7.16), and the entry point of the egress cannula is identified (Figure 7.17). Once orientation is achieved, continued retraction of the telescope allows visualization of the caudal articular surface of the patella, the cartilage of the trochlear groove, the medial trochlear ridge, and the medial parapatellar fibrocartilage (Figure 7.18). The telescope is directed into the proximal medial compartment of the joint (Figure 7.19), retracted distally in the medial compartment (Figure 7.20), and then transferred to the lateral compartment (Figure 7.21) for evaluation of the abaxial surfaces of the trochlear ridges and the joint capsule. These areas are examined with the joint in extension. Figure 7.11 The view with the telescope in the distended suprapatellar pouch looking proximally from a craniomedial portal. The image is almost completely filled with the smooth, almost translucent distended joint capsule. Blood vessels are visible in the joint capsule tissue. The small area of white in the bottom‐right edge of the image is the proximal end of the trochlear groove joint cartilage. Cranial is up on the image. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.12 Orientation in the stifle joint with the tip of the telescope in the suprapatellar pouch looking proximally from a craniomedial portal and cranial is up on the picture. Visible are the joint capsule, a single horizontal band or plica crossing the center of the image, and the caudal surface of the quadriceps tendon at the top of the picture. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.13 A partially distended stifle joint with a single horizontal plica in contact with the caudal surface of the quadriceps tendon above the plica. The proximal end of the patella is visible at the top of the image and the trochlear groove at the bottom of the image. Cranial is up on the image with the telescope looking proximally from a craniomedial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.14 A normal variation is seen in this patient with multiple plicae in the suprapatellar pouch of a fully distended stifle joint. Telescope position and orientation are the same as the previous image. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.15 Retraction of the telescope from the suprapatellar pouch brings the proximal trochlear groove into view at the bottom of the image and caudal surface of the proximal patella at the top of the image. The suprapatellar pouch and the caudal surface of the quadriceps tendon are still visible in the field at the top of the image. Orientation and telescope position are the same as in the previous images. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.16 A normal accumulation of fat visible in the suprapatellar pouch proximal to the trochlear groove articular cartilage. The telescope is looking proximally from a craniomedial portal with cranial up on the image. The proximal extent of the trochlear groove is visible at the bottom with the quadriceps tendon at the top, joint capsule in the background with an indistinct plica, and fat at the bottom center of the picture. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.17 The entry point of the egress cannula seen in the lateral extent of the suprapatellar pouch in a normal joint. Lateral is to the right with cranial up on the image, and the telescope is looking craniolaterally from a craniomedial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.18 The trochlear groove is seen at the bottom of the image with the lateral trochlear ridge on the right, the caudal articular surface of the patella at the top, the medial trochlear ridge in the left foreground, and the medial parapatellar fibrocartilage in the background at the top left of the image to the left of the patella. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.19 The proximal end of the medial joint space with joint capsule curving across the top of the image and down the left side with the proximal end of the medial aspect of the medial trochlear ridge to the right. A small accumulation of fat is visible attached to the medial joint capsule. The tip of the telescope has been moved from the trochlear groove into the medial joint space and is looking proximally from a craniomedial portal. Cranial is up, and medial is to the left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.20 Further distally in the medial joint space from the image in the previous figure, the medial surface of the medial trochlear ridge is visible on the right and medial joint capsule is seen on the left side of the image. From the craniomedial portal, the telescope is aligned with the medial joint space allowing easy examination. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.21 Lateral joint space with the lateral surface of the lateral trochlear ridge viewed on the left with the telescope angled across the trochlear ridges from the craniomedial telescope portal. Lateral joint capsule is seen filling the right side of the image. Medial is to the left, and cranial is up. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. The telescope is positioned in the inter‐condyloid fossa for evaluation of the cranial and caudal cruciate ligaments (Figure 7.22a). Occasionally, the middle genicular artery is seen in the space between the fat pad and the cruciate ligaments (Figure 7.22b). Visualization of the medial meniscus is achieved by external rotation of the tibia with valgus stress to the stifle to open the medial joint space. The entire meniscus can be examined from the cranial pole (Figure 7.23), moving medially and caudally to visualize the axial margin (Figure 7.24), caudal pole (Figure 7.25), and the caudal meniscotibial ligament of the medial meniscus (Figure 7.26). The lateral meniscus is exposed by varus stress to the stifle, with or without internal rotation, for examination of the cranial pole and cranial portion of the axial margin (Figure 7.27), moving caudally to visualize the caudal portion of the axial margin (Figure 7.28), the caudal pole (Figure 7.29), and the caudal tibial ligament of the lateral meniscus (Figure 7.30). The meniscofemoral ligament of the lateral meniscus can occasionally be seen. If there is significant drawer instability because of a cranial cruciate ligament injury, visualization of the meniscuses is improved by cranial displacement of the proximal tibia. The long digital extensor tendon is identified in the craniolateral joint and is visualized from its origin at the extensor fossa on the abaxial surface of the lateral condyle of the femur to where it exits the joint distally. Its appearance changes based on position of the joint and the telescope portal being used, from what is seen with the telescope in the craniomedial portal and the joint at a standing position (Figure 7.31), with the joint fully flexed (Figure 7.32), and with the joint fully extended (Figure 7.33). When the telescope is in the craniolateral portal, it is directly over the long digital extensor tendon (Figure 7.34). The proximal tendon of origin of the popliteal muscle is also identified in the lateral compartment of the joint, when the telescope is in the craniolateral portal, and the telescope is passed through the triangular space between the femoral condyle and the long digital extensor tendon (Figure 7.31). The tendon is seen from its origin on the lateral aspect of the lateral femoral condyle as it angles caudally and distally (Figure 7.35) and can be followed as it extends into the caudal joint space (Figure 7.36). The caudal compartment of the stifle joint can also be accessed by passing the telescope through the intercondyloid fossa through the space created by a ruptured cranial cruciate ligament. Placement of the telescope into the caudal joint space using this approach is not attempted when the cruciate ligaments are intact as ligament damage can occur. Figure 7.22 (a) Normal cranial and caudal cruciate ligaments. The cranial cruciate is seen on the left side of the image with the fibers directed toward the telescope. The caudal cruciate ligament is on the right side of the image with the fibers running more vertically. The telescope is looking caudally from a craniomedial telescope portal with proximal or dorsal up on the image and medial is to the right. (b) A view of the cranial joint space with the fat pad displaced ventrally and the middle genicular vessels supplying the fat pad are seen coursing across the center of the image between the caudal surface of the fat pad at the bottom, the craniolateral surface of the medial femoral condyle on the left, and the caudal cruciate ligament deep on the right. The cranial cruciate ligament is not visible as it is buried in the fat pad. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.23 The cranial pole of the medial meniscus is in the lower left of the image with the tibial plateau at the bottom on the right and the medial femoral condyle filling the top half of the image. The telescope is looking caudomedially from a craniomedial portal with medial to the left and dorsal or proximal up. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.24 The axial margin of a normal medial meniscus seen on the left side of the joint space crossing the tibial plateau at the bottom. The medial femoral condyle is visible at the top of the image. Undulations present in the free margin are normal and are positional artifacts created by cranial displacement of the tibial plateau relative to the femur. The tip of a 2.0 mm manipulation probe is seen at the far right of the image. The telescope is looking caudomedially from a craniomedial portal with medial to the left and dorsal or proximal up. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.25 The caudal pole of the medial meniscus is on the left‐center of the image transitioning into the caudal tibial ligament of the medial meniscus on the right‐center of the image. The medial femoral condyle is in the upper left of the image, and the tibial plateau is at the bottom of the image. The tip of a 2.0 mm manipulation probe is visible at the far right of the image. The telescope is looking caudomedially from a craniomedial portal with medial to the left and dorsal or proximal up. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.26 The caudal tibial ligament of the medial meniscus is seen obliquely crossing the center of the image with the caudal cruciate ligament on the right, the caudolateral corner of the medial femoral condyle on the upper left, and the tibial plateau on the bottom. The transition into the caudal pole of the medial meniscus is seen at the left end of the ligament. The telescope is looking caudally from a craniomedial portal with medial to the left and dorsal or proximal up. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.27 The cranial pole and cranial portion of the axial margin of the lateral meniscus is seen on the left of the image between the lateral femoral condyle at the top of the image and the tibial plateau at the bottom. The lateral meniscus is less likely to distort with undulations see in the medial meniscus. The telescope is looking caudolaterally from a craniomedial portal with lateral to the left and dorsal or proximal up. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.28 The central and caudal axial margin of the lateral meniscus on the right and deep in the image seen between the lateral femoral condyle in the upper left and the tibial plateau at the bottom. Mild irregularity or fraying of the axial margin seen in this lateral meniscus is not uncommon and is not considered to be clinically significant. The telescope is looking caudolaterally from a craniomedial portal with lateral to the right and dorsal or proximal up. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.29 The ventral surface of the caudal pole of the lateral meniscus is crossing the center of the image. The meniscus is being elevated with a 2.0 mm hook probe to assess its ventral surface. The lateral femoral condyle is filling the upper half of the image, and the tibial plateau is on the bottom. The telescope is looking caudally from a craniomedial portal with medial to the left and dorsal or proximal up. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. In the presence of significant stifle pathology with typical villus synovial reaction, visualization of the stifle is greatly facilitated by partial cranial compartment synovectomy and fat pad removal using a combination of radiofrequency and a power shaver before examination of the cruciate ligaments or meniscuses. Extensive villus synovial proliferation is seen with cruciate ligament injuries and since this is the most common diagnosis with arthroscopy of the stifle joint, this is a very important step in the procedure. In normal joints, examination can be completed in most cases without fat pad resection. Radiofrequency in this application has the advantage of sealing blood vessels during tissue removal but has the disadvantage of leaving more debris in the joint (Figure 7.37). The shaver has the advantage of leaving little or no debris in the joint but does not control bleeding. Without hemostasis bleeding obscures, the visual field preventing examination or operative procedures. Thus, the shaver is used primarily to remove avascular tissue such as the fat pad, cruciate ligament, and meniscal tissue. The combination of both instruments minimizes the disadvantages of each and applies the advantages of both. Figure 7.30 The caudal pole of the lateral meniscus is seen deep to the lateral femoral condyle with the caudal tibial ligament of the lateral meniscus deep on the left side of the image. Most of the axial margin of the lateral meniscus is visible with the tip of the cranial pole indistinctly seen at the right margin of the image. The lateral femoral condyle is at the top of the image, and the caudomedial margin of the tibial plateau is visible in the bottom center of this view. The telescope is looking caudally from a craniomedial portal with medial to the left and dorsal or proximal up. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.31 The tendon of origin of the long digital extensor muscle is seen extending distally from its origin on the abaxial surface of the lateral femoral condyle. In this image, the joint is at a normal standing angle and the telescope is looking laterally from the craniomedial portal. The craniolateral aspect of the lateral femoral condyle is on the left side of the image, the long digital extensor tendon is visible crossing the center of the image vertically, and the joint capsule is on the right. Lateral is to the right and dorsal or proximal is up. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.32 The tendon of origin of the long digital extensor muscle is seen with the joint fully flexed and with the telescope looking laterally from the craniomedial portal. The tendon is positioned vertically in the center of the image, the femoral condyle is on the left and the lateral joint space is on the right. The surface of the tendon is mildly roughened without the smooth clean surface and easily seen tight fibers seen in the previous image indicating possible early injury. Lateral is to the right, and dorsal or proximal is up. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.33 The tendon of origin of the long digital extensor muscle is seen with the joint extended with the telescope looking laterally from the craniomedial portal. The tendon is seen as a vertical structure in the center of the image with the lateral margin of the lateral femoral condyle filling the upper left, the caudal surface of the fat pad at the bottom of the image, and the lateral joint capsule on the right. This tendon does not have a totally normal appearance. Lateral is to the right, and dorsal or proximal is up. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.34 The tendon of origin of the long digital extensor muscle seen with the telescope in the craniolateral portal. Medial is to the right, and proximal or dorsal is up. The lateral femoral condyle is seen on the right side of the image with the tendon filling the left side of the image. A small portion of the abaxial margin of the lateral meniscus and its articulation with the lateral femoral condyle are visible in the lower right of the image cranial to the tendon. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.35 The popliteal tendon is seen in the lateral joint space originating from the abaxial surface of the lateral femoral condyle and running caudally and distally within the joint. The tendon is obliquely positioned in the center of the image with the lateral femoral condyle in the upper left, the abaxial surface of the lateral meniscus on the lower left, and the lateral joint capsule on the right. The telescope is looking caudally from a craniolateral portal with dorsal or proximal up and lateral is to the right. To obtain this view, the telescope is passed between the long digital extensor tendon and the femoral condyle. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.36 The popliteal tendon can be followed caudally as it extends around the caudolateral corner of the joint into the caudal joint compartment. The tendon is seen as it obliquely crosses the upper image with the caudal portion of the lateral femoral condyle on the upper right, the caudal abaxial margin of the lateral meniscus on the lower right, and joint capsule on the left. The joint capsule in this image shows an abnormal appearance with villus ghosts indicating resolved inflammation. The telescope is looking caudally from a craniolateral portal with dorsal or proximal up, and lateral is to the left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.37 Debris remaining after using radiofrequency to debride the origin of a ruptured cranial cruciate ligament. The caudal cruciate ligament is visible on the left side of the image, and the lateral surface of the medial femoral condyle is on the right. The irregular dirty tissue in the center of the image is the remaining debrided end surface of the cranial cruciate ligament. The telescope is looking caudolaterally from a craniomedial portal with medial to the left and dorsal or proximal up. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Partial or complete rupture of the cranial cruciate ligament is the most common pathology found with arthroscopy in the stifle joint of dogs. The initial finding on entering a stifle joint with cruciate ligament pathology is an extensive villus synovial reaction throughout the joint. Typically this villus reaction is dramatic and is seen in the suprapatellar pouch (Figure 7.38), the medial joint space (Figure 7.39), the lateral joint space (Figure 7.10), the caudal joint compartment (Figure 7.40), and in the cranial joint compartment (Figure 7.41). This villus synovial reaction is present on all synovial surfaces of the joint and is involved in all joint spaces with equal severity. Variation in severity of synovitis is not based on location in the joint but is based on other factors such as chronicity. Mild early synovial reaction is seen in all the above joint spaces (Figures 7.42–7.44). Synovial reaction in the stifle joint of dogs with cranial cruciate ligament injuries also has other less common appearances including smooth nodules (Figure 7.45), nodular roughening with vascular (Figure 7.46) or avascular appearance (Figure 7.47), single nodules (Figure 7.48), large thick smooth synovial projections with vascularity (Figure 7.49) or without apparent blood vessels (Figure 7.50), multiple mass‐like lumps (Figure 7.51), single (Figure 7.52) or multiple (Figure 7.53) large irregular fronds with or without visible vascular supply, low flat areas of synovial thickening (Figure 7.54), and combinations of these formations (Figure 7.55). The villus synovial reaction seen with cruciate ligament disease, and other joint pathology, is typically very vascular but when the active reaction resolves villus “ghosts” are left behind and are seen in all the areas where villus reaction occurs (Figures 7.56 and 7.57). Figure 7.38 Villus synovial reaction in the suprapatellar pouch of a dog with a cranial cruciate ligament injury. The telescope is looking proximally from a craniomedial portal with medial to the left. There are no anatomically identifiable structures in this picture which is typical in areas of joints with cranial cruciate ligament injuries. Villus reaction in this picture has two different appearances. The villi with obvious blood vessels on the left are originating from the joint capsule and those on the right without visible blood vessels are coming off the periosteum proximal to the trochlear articular cartilage. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.39 Typical villus synovial reaction in the medial joint space of a dog with a cranial cruciate ligament rupture. Medial is to the right, and the telescope is looking proximally or dorsally from a craniomedial portal. A ridge of osteophytes is visible in the upper left side of the image with prominent villi containing obvious blood vessels coming off femoral periosteum on the lower left and scattered small villi coming off the joint capsule in the upper right half of the image. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.40 Villus synovial reaction in the caudal joint compartment of a dog with a cranial cruciate ligament rupture. The telescope is looking caudally through the intercondyloid fossa of the femur from a craniomedial portal. Access to the caudal joint space in this patient was easily achieved because the cranial cruciate ligament was completely ruptured. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.41 Villus synovial reaction in the cranial joint compartment of a dog with a cranial cruciate ligament rupture. Strands of the ruptured cruciate ligament are seen in the background. The telescope is looking caudally from a craniomedial portal and dorsal or proximal is up on the image. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.42 Mild synovial reaction in the suprapatellar pouch in a dog with early partial cranial cruciate ligament rupture. Cranial is up on the image, and the telescope is looking dorsally or proximally from a craniomedial portal. Anatomic structures are still visible and are not obscured with synovial reaction. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.43 Very mild synovial reaction on the joint capsule surface of the medial joint space in a dog with very early partial cranial cruciate ligament rupture. The telescope is looking proximally from a craniomedial portal with cranial up on the image and medial is to the left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.44 Early very mild synovial reaction in the cranial joint space among strands of ruptured cranial cruciate ligament. The telescope is looking caudally from a craniomedial portal with proximal or dorsal up and medial is to the right. The lateral surface of the medial condyle fills the right side of the image. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.45 Scattered nodules of smooth synovial thickening without villi formation in the stifle of a dog with a very early partial cranial cruciate ligament injury. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Synovial membrane petechiae are seen in canine stifle joints with cranial cruciate ligament injuries. These lesions have been observed in the suprapatellar area at the proximal end of the trochlear groove (Figure 7.58), on the distal end of the patella (Figure 7.59), and in the intercondylar fossa (Figure 7.60). Larger more ecchymotic lesions have also been seen (Figure 7.61). The cause and significance of these lesions are unknown. Figure 7.46 Nodular roughening of the synovium with visible vascularity in the stifle of a dog with a cranial cruciate ligament injury. The telescope is looking proximally in the medial joint space with medial joint capsule on the left and femur on the right obscured by the synovial reaction. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.47 Avascular nodular roughening of the synovium in a dog stifle with cranial cruciate ligament disease. The telescope is looking proximally in the medial joint space with the avascular nodular roughening on the femur on the right and more vascular joint capsule in the background to the left. Cranial is up on the image. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.48 A single small synovial mass in the medial joint space of the stifle joint in a dog with a cranial cruciate ligament injury. The mass is originating from the femoral surface on the left side of the image with variable severity typical villus reaction on the remainder of visible synovial surfaces. The telescope is looking proximally from a craniomedial portal with cranial up and medial to the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.49 A large smooth vascular synovial projection in the suprapatellar pouch in a dog’s stifle joint with a ruptured cranial cruciate ligament. Multiple synovial masses are also present in the background. Cranial is up on the image, and the telescope is looking proximally from a craniomedial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Osteophytes are seen at the margins of articular surfaces as part of degenerative changes secondary to CCL injuries. A common site for stifle osteophytes is in the suprapatellar pouch extending proximal to the articular surface of the trochlear groove as relatively flat extension of the cartilage surface with varying grades of chondromalacia (Figure 7.74), as multiple irregular rounded bony proliferations with shallow separations giving a “cobble stone” appearance (Figure 7.75), multiple rounded bony proliferations in the same area with deep grooves separating lesions (Figure 7.76), as a rim of osteophytes around a recessed area without bony proliferation (Figure 7.77), as a transverse ridge of bone proximal to the trochlear groove cartilage (Figure 7.78), as flat(Figure 7.79) or elevated (Figure 7.80) extensions medially or laterally (Figure 7.81), and as isolated bony elevations (Figure 7.82). Osteophytes also occur on the medial and lateral surfaces of the trochlea at the abaxial cartilage margins as small low flat ridges of bone (Figure 7.83), as large smooth round ridges (Figure 7.84), and as large irregular round ridges (Figure 7.85) viewed with the telescope positioned in the medial joint space from the craniomedial telescope portal. Medial osteophytes are also seen with the telescope positioned in the trochlear groove or cranial to the medial joint space as large mildly irregular round ridges (Figure 7.86), or as flattened ridges (Figure 7.87). Similar abaxial osteophytes are also seen on the lateral aspect of the femoral trochlea having the same variation in appearance with small (Figure 7.88), large smooth ridges (Figure 7.89), large irregular ridges (Figure 7.90), large irregular clusters (Figure 7.91), and flattened lesions (Figure 7.92). As seen in the previous images, osteophytes on the distal femoral condyle typically occur at the margins of articular cartilage surfaces but they can also occur within the articular cartilage (Figures 7.93 and 7.94). Patellar osteophytes are seen at the proximal end (Figure 7.95), the distal end (Figure 7.96), on the medial (Figure 7.97) or lateral (Figure 7.98) margins, or in multiple locations (Figure 7.99). Osteophytes are less commonly seen on the tibial plateau in the area of the intercondyloid eminence (Figure 7.100) and in the intercondyloid fossa of the femur (Figure 7.101). All the above images show hard osteophytes comprised of bone in various sizes, locations, and configurations and it has always been assumed that osteophytes form as bone at their origin and throughout their growth. One case was seen with soft tissue formations in the area on the abaxial surface of the femoral condyle where osteophytes typically form (Figure 7.102) suggesting the possibility that osteophytes originate as soft tissue that becomes bone with maturation. Figure 7.50 A large avascular smooth synovial projection in the suprapatellar pouch of the stifle joint in a dog with a cranial cruciate ligament injury. Villus ghosts are also visible in this image and the avascular appearance of the large lesion may be related to the ghost stage in this stifle. The telescope is looking proximally from a craniomedial portal with cranial up on the image. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.51 Multiple synovial masses in the suprapatellar pouch of the stifle joint in a dog with a chronic cranial cruciate ligament rupture. Some of the masses are white, avascular in appearance and others have a more vascular coloration but no blood vessels are visible. Cranial is up in this picture, and the telescope is looking proximally from a craniomedial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.52 A single large irregular synovial frond in the suprapatellar pouch of a dog stifle joint with a chronic cranial cruciate ligament injury. The low vascularity of this tissue may indicate resolution of the active phase or may be due to other factors. Villi in the lower left background have more coloration indicating a more active process. The telescope is looking proximally from a craniomedial portal and cranial is up. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.53 Multiple large irregular synovial fronds in the suprapatellar pouch of a stifle joint of a dog with a chronic cranial cruciate ligament rupture. Cranial is up in this picture, and the telescope is looking proximally from a craniomedial portal. Vascularity appears to increase from left to right but the significance of this is unclear. Villi in the background have a red, vascular coloration. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.54 A wide‐based flat area of synovial thickening in the suprapatellar pouch at the proximal end of the visible quadriceps tendon of a dog stifle joint with a chronic cranial cruciate ligament injury. There are multiple villus ghosts scattered over the joint capsule surface indicating an inactive process. A plica is partially visible extending across the background of the image. Cranial is up with the telescope looking proximally. The proximal end of trochlear groove cartilage is visible across the bottom of the picture with an area of mildly reactive discolored synovium in the bottom center. Multiple proximal trochlear osteophytes are present across the lower center of the image proximal and abaxial to the bottom center area of synovial reaction. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.55 A combination of the previously described synovial changes in the stifle joint in the suprapatellar pouch of a dog with a cranial cruciate ligament rupture. Villi with visible blood vessels, villi without visible vessels, a mass, fronds, and villus ghosts are all present. Cranial is up, and the telescope is looking proximally from a craniomedial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.56 Villus “ghosts” in the suprapatellar pouch of the stifle of a dog with a cranial cruciate ligament rupture. The telescope is looking proximally from a craniomedial portal and cranial is up. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.57 Villus “ghosts” in the cranial joint compartment of the stifle of a dog with a cranial cruciate ligament injury. Dorsal or proximal is up on the image, and the telescope is looking caudally from a craniomedial portal. Femoral condyle articular cartilage is seen in the background across the top of the picture. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.58 Petechia in the synovial membrane at the proximal end of the trochlea is seen across the bottom of the image in a dog with a cranial cruciate ligament injury. Cranial is up, and the telescope is looking proximally. Villus synovial reaction is present in the suprapatellar pouch in the upper background. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.59 Petechia in the synovium at the distal end of the patella in a dog with a cranial cruciate ligament injury. Cranial is up, and the telescope is looking proximally from a craniomedial portal. The distal end of the patella is visible in the center of the image with the caudal articular patellar surface extending into the background in the lower right and the synovial covered caudal surface of the patellar tendon seen across the top of the picture. A small area of parapatellar cartilage is visible on the far left with petechia on its distal surface. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.60 Petechia in the synovial membrane on the axial surface of the intercondylar fossa in the stifle of a dog with cranial cruciate ligament disease. The telescope is looking caudally from a craniomedial portal. Proximal or dorsal is up on the picture, and the caudal cruciate ligament is visible on the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.61 A larger area of synovial hemorrhage more on the size of an ecchymosis is seen in the synovial tissue at the proximal end of the trochlear groove in the lower left. Cranial is up, and the telescope is looking proximally. The suprapatellar pouch is seen in the upper background with an area of villus reaction. Proximal trochlear groove osteophytes are seen in the center proximal to the area of the ecchymosis and on the trochlear ridge on the right side of the picture. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.62 Vascular pannus extending onto the proximal articular cartilage of the trochlear groove in the stifle of a dog with cranial cruciate ligament disease. Cranial is up, and the telescope is looking proximally. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.63 Vascular pannus in a cartilage indentation on the ventral or distal surface of the medial condyle of the femur. The bed of this indentation was covered with normal‐appearing cartilage. The cause of this lesion is unknown but is in the location typical for OCD. The femoral condyle fills the upper right of the image with tibial plateau across the bottom. The telescope is angled caudomedially from a craniomedial portal with proximal or dorsal up and medial to the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.64 Vascular pannus on the margin of the articular cartilage of the patella in a dog with a cranial cruciate ligament injury. Cranial is up and proximal is to the right with the telescope looking at the medial surface of the patella from a craniomedial portal. The patella fills the upper portion of the picture, and the trochlear groove articular cartilage is visible in the lower right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.65 Vascular pannus on multiple structures including the axial surface of the intercondylar fossa of the femur on the left and the caudal cruciate ligament on the right. This is seen in the stifle joint of a dog with a cranial cruciate ligament rupture. Proximal is up, and the telescope is looking caudally from a craniomedial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Cartilage lesions seen with cranial cruciate ligament disease include all grades of chondromalacia (Table 3.1) and are seen on all articular cartilage surfaces throughout the joint. Mild or Grade I chondromalacia has been seen as single blisters on the femoral condyles (Figure 7.103) and in the trochlear groove (Figure 7.104), as multiple blisters or swelling on the caudal surface of the patella (Figure 7.105) and in the trochlear groove (Figure 7.106), and as swelling of the tibial plateau cartilage (Figure 7.107). Grade II chondromalacia of articular cartilage occurs on the femoral condyles as focal (Figure 7.108) or diffuse (Figure 7.109) fibrillation, fibrillation on the tibial plateau (Figure 7.110), in the trochlear groove as fibrillation (Figure 7.111) or superficial mild fissures with fibrillation (Figure 7.112), and on the caudal surface of the patella as fine fibrillation (Figure 7.113) or erosions (Figure 7.114). More severe chondromalacia, Grade III, is also seen in all areas of the stifle joint with lesions occurring in the trochlear groove as fibrillation (Figure 7.115), fissures (Figure 7.116), and erosions (Figure 7.117); fibrillation (Figure 7.118) and erosions (Figure 7.119) on the caudal surface of the patella; femoral condyle lesions with erosions (Figure 7.120), coarse fibrillation (Figure 7.121), or fine fibrillation (Figures 7.122 and 7.123); and on the tibial plateau (Figure 7.124). Grade IV chondromalacia has most commonly been seen on the femoral condyle as a focal area of depressed roughened cartilage with full‐thickness fissures (Figure 7.125) or as focal full‐thickness cartilage loss with either fibrillated or fractured cartilage debris within the defect (Figure 7.126). These lesions are located and have the appearance suspiciously similar to chronic untreated OCD. Full‐thickness cartilage loss with exposed eburnated bone, Grade V chondromalacia, is not commonly seen in the stifle joint but can occur on the femoral condyle and tibial plateau with chronic untreated cranial cruciate ligament rupture (Figure 7.127). Figure 7.66 Vascular pannus on the dorsal surface of the medial meniscus in a dog with a cranial cruciate ligament rupture. This is the stifle of the dog with pannus in a cartilage indentation on the femoral condyle shown in Figure 7.63, and the pannus lesion is seen in the upper right of the picture. Damaged meniscus is seen extending across the center of the image immediately below the articular surface with the pannus lesion on the meniscus in the lower right. Proximal or dorsal is up on the image, and the telescope is looking caudomedially from a craniomedial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.67 Vascular pannus on the articular cartilage surface of an osteophyte on the abaxial surface of the medial femoral trochlear ridge. The telescope is looking proximally from a craniomedial portal with cranial up and medial to the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.68 Mild vascular pannus on the long digital extensor tendon in the stifle of a dog with a cranial cruciate ligament injury. The telescope is looking laterally from a craniomedial portal with proximal or dorsal up and lateral to the right. The craniolateral portion of the lateral femoral condyle fills the left side of the picture with the long digital extensor tendon seen as a vertical band in the center, and reactive joint capsule along the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.69 Marked vascular pannus on the long digital extensor tendon in the stifle of a dog with a cranial cruciate ligament injury. The long digital extensor tendon fills the center of the image with a small portion of femoral condyle on the left and joint capsule on the right. Orientation is the same as the previous image. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.70 Vascular pannus on the surface of an apparently intact cranial cruciate ligament. There was a very early partial rupture that was not visible in this image but was visible on the caudomedial corner of the ligament. Proximal or dorsal is up on the image and lateral is to the left. The caudal cruciate ligament is visible in the upper right side of the picture and fat pad is in the lower right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.71 Vascular pannus on a loose completely ruptured cranial cruciate ligament. The cruciate ligament almost completely fills the image with a small portion of femoral condyle visible in the upper left. Proximal or dorsal is up, and medial is to the right with the telescope looking caudally from a craniomedial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.72 Vascular pannus on the caudal cruciate ligament in a dog with a cranial cruciate ligament rupture, vertical splitting of the caudal cruciate ligament, and visible transverse striations indicating that the ligament is loose. Dorsal or proximal is up on the image. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.73 The vascular pannus lesion seen in Figure 7.62 when increased intra‐articular pressure has compressed the blood vessels making the lesion less distinct. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 7.74 Osteophytes in the suprapatellar pouch proximal to the cartilage of the trochlear groove appearing as a relatively flat smooth extension of cartilage with Grade III chondromalacia. The telescope is looking proximally, and cranial is up on the image. Source: Timothy C. McCarthy. © John Wiley & Sons Inc.
7
Stifle Joint
The argument for meniscal release does not apply to all joints and to all meniscal release techniques. The original release technique performed with TPLO surgery using a radial midbody meniscotomy violates the principles of meniscal surgery and is not recommended (Video 7.1), whereas transecting the caudal tibial ligament of the medial meniscus leaves the meniscal body intact and reduces the impact of losing the mechanical support of a normal meniscus. If we accept that meniscal release may reduce joint pain or the risk of future meniscal injury then the question is, when is meniscal release indicated and when is it not indicated. If there is a complete rupture of the cranial cruciate ligament with significant instability of the joint, then there is arguably an indication for meniscal release. If there is an early partial tear of the cranial cruciate ligament with a significant portion of the ligament remaining intact and minimal or no instability releasing the meniscus is not indicated. Second‐look arthroscopy in cases of partial cruciate ligament injuries that had a TPLO have shown that with removal of the repetitive tibial thrust stress during weight‐bearing the ligament can heal. When this happens, the end result is a normal or nearly normal joint. This is the ideal result for cranial cruciate ligament injuries.
7.1 Patient Preparation, Positioning, and Operating Room Setup
7.2 Portal Sites and Portal Placement
7.2.1 Telescope Portal
7.2.2 Operative Portals
7.2.3 Egress Portal
7.3 Nerves of Concern with Stifle Joint Arthroscopy
7.4 Examination Protocol and Normal Arthroscopic Anatomy
As the tip of the telescope moves distally around the cranial aspect of the femoral condyles, either medial or lateral, the joint is flexed. The tip of the telescope can also be moved distally in the trochlear groove after the medial and lateral compartments have been examined. The fat pad is encountered during this portion of the examination and in normal joints can be swept out of the visual field with the tip of the telescope allowing examination of the cranial surface of the femoral condyle. The visual field is commonly lost during this maneuver due to the fat pad. If this occurs, the telescope is repositioned in the medial or lateral joint space and the maneuver is repeated until the image is maintained. Examination around the fat pad is much more difficult in the presence of the typical villus synovial reaction seen with cranial cruciate ligament injuries, but cursory examination can still be achieved in some patients (Video 7.2). Partial synovectomy and fat pad resection are needed for effective examination of joints with pathology.
7.5 Diseases of the Stifle Joint Diagnosed and Managed with Arthroscopy
7.5.1 Cranial Cruciate Ligament Injuries
Vascular pannus is also seen in stifle joints with cranial cruciate ligament disease (Video 2.1). As with petechia, their cause and significance are not known but they are likely a manifestation of synovial proliferation extending over cartilage, ligaments, menisci, and other surfaces. Pannus cannot form on articular cartilage surfaces if there is normal weight‐bearing contact as the normal contact forces destroy the blood vessels and tissue. This could potentially be a source of joint pain and hemarthrosis. Lesions are seen on articular cartilage surfaces in the proximal trochlear groove (Figure 7.62), on the femoral condyle (Figure 7.63) and on the patella (Figure 7.64). Pannus lesions are also seen on areas other than articular cartilage including the axial surface of the intercondylar fossa (Figure 7.65), on menisci (Figure 7.66), on osteophytes (Figure 7.67), on the long digital extensor tendon (Figures 7.68 and 7.69), and on both the cranial (Figures 7.70 and 7.71) and caudal cruciate ligaments (Figure 7.72). The appearance of pannus lesions is affected by intra‐articular pressure with increased pressure compressing the blood vessels making them less distinct (Figure 7.73) (Video 2.1).
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