Osteoarthritis (OA) is one of the most debilitating musculoskeletal disorders among equine athletes. It is a progressive disease characterized by joint pain, inflammation, synovial effusion, limited range of motion, and a progressive deterioration of articular cartilage. Unremitting joint pain and inflammation often cause adaptive muscle guarding and altered weight bearing to protect the affected limb from further discomfort and injury. In humans, compensatory changes in posture and movement exacerbate the initial joint injury, which cause further alterations in limb biomechanics and contribute to the progression of OA. Similar compensatory mechanisms such as altered muscle activation patterns, increased joint stiffness, and a redistribution of limb loading, are likely to also occur in horses.

Physical rehabilitation has become an effective treatment option for reducing or limiting harmful compensatory gait abnormalities in humans. Rehabilitation programs that address OA and musculoskeletal injuries often incorporate some form of aquatic exercise. Exercising in water provides an effective medium for increasing joint mobility, promoting normal motor patterns, increasing muscle activation, diminishing limb edema, and reducing the incidence of secondary musculoskeletal injuries due to primary joint pathology. Underwater treadmill exercise has become an increasingly popular therapy for the rehabilitation of equine musculoskeletal injuries; unfortunately, there is no scientific evaluation of its effectiveness for the treatment of OA. This project was established to investigate the physiologic, biomechanical, and histologic effects of aquatic therapy on diminishing the progression of OA within the equine middle carpal joint. Results from this study will provide an objective assessment of the pathologic characteristics associated with OA and the potential clinical and disease-modifying effects allied with aquatic therapy.