Chapter 32 Diseases of the Musculoskeletal System
Disorders of the musculoskeletal system are common in pet birds. Trauma is a frequent cause of these disorders, although many systemic diseases also involve this system. Malnutrition, metabolic diseases, parasites, and neoplasia can all affect the musculoskeletal system.
The skeletal anatomy of avian species is well developed for flight. Bones are lightweight, air-filled structures (pneumatic bones), other structures are fused for increased rigidity, the keel bone is adapted for support of the large pectoral muscles, and flight muscles have an increased anaerobic metabolic ability. However, the same structures that are so useful in flight also predispose the avian animal to traumatic injuries.
Traumatic injuries include both soft- and bony-tissue damage. Soft-tissue injuries frequently involve bite wounds, either from other birds or from mammalian pets in the household. Cat bites can be extremely problematic because they are commonly associated with Pasteurella multocida infections and a guarded prognosis. Injuries from falls during flight are also common. Heavy-bodied birds with extensive wing trims often land hard on the sternum, splitting the skin and damaging the underlying muscles. Traumatic wing or leg injuries may occur while flying, landing, or playing in the cage. Ceiling fans are particularly dangerous for flying birds. Self-mutilation occurs in several species of birds, most commonly cockatoos (the sternum), lovebirds, conures, Quaker parakeets (the flank and axilla), and Amazon parrots (the feet). The cause of this problem is poorly understood.
Lameness in pet birds may be due to many causes. Fractures/luxations, joint infections, metabolic diseases, trauma, neoplasia, and nutritional problems can all cause lameness. Fractures or luxations are frequently the result of trauma. The onset of the lameness is usually acute. Septic joints will appear swollen and painful with or without bone involvement. Lameness as a result of metabolic disease or neoplasia may have a slower onset or appear to be acute.