Chapter 98Experiences Using a High-Speed Treadmill to Evaluate Lameness
The advent of the high-speed treadmill has led to many advances in evaluating equine poor performance in exercise physiology, gait analysis, cardiac disease, and lameness diagnosis.1-5 This chapter describes our experience using a high-speed treadmill for lameness evaluation in the performance horse.
Lameness has been implicated as a cause of poor performance in several studies involving a complete physical examination, lameness examination, and where possible a high-speed treadmill examination.1-3 In one study, 74% of horses were found to have lameness as a component of poor performance.1 In another study, in which horses with no apparent history of lameness were examined because of poor performance, clinically important lameness in 23.9% of horses precluded a high-speed treadmill investigation.2 In a third study, 4.3% of horses sound enough to undergo a high-speed treadmill examination for poor performance were clinically significantly lame after high-speed treadmill exercise.3
In our experience, convincing trainers and owners that lameness is a cause for poor performance can be difficult. Several studies using a shoe model to induce lameness to assess the metabolic cost of pain related to lameness suggested a trend that pain related to lameness may not increase the metabolic cost of exercise, but it does increase the heart rate in response to pain.6-8 However, another study suggested that a metabolic cost of pain and exercise does occur.9 Pain may alter a horse’s ability or willingness to perform up to expectations or previous performance levels.10
Criteria for Case Selection
The most common criterion for a treadmill lameness examination is lameness that occurs at only high speeds or after an extended period of exercise. The treadmill examination is used most commonly in Standardbred (STB) racehorses or endurance horses. However, a treadmill lameness examination can be used in any breed or discipline, although a horse in which lameness is apparent only when the horse is ridden may be unsuitable.
Horses in which a complete lameness investigation, including diagnostic analgesia and appropriate imaging technologies, fails to reveal a diagnosis are potential candidates for treadmill lameness examination. Additional candidates include horses that require considerable work at low, medium, or higher speeds before the lameness becomes apparent, such as endurance horses or STB racehorses. A treadmill lameness examination also may be useful in horses that are fractious or otherwise pay little attention when jogged in hand or ridden. Horses must pay close attention when trotting on a treadmill and therefore have a more even, rhythmical, relaxed gait that is easier to evaluate.
History
Important historical facts need to be ascertained. Some questions are general, and some are use related. Some may need to be repeated in a different order to elicit an accurate answer. Questions may include those listed in Box 98-1.
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