Clinical effects of exercise on subchondral bone of carpal and metacarpophalangeal joints in horses

Objective-To determine effects of treadmill exercise on subchondral bone of carpal and metacarpophalangeal joints of 2-year-old horses. Animals-12 healthy 2-year-old horses. Procedure-Horses were randomly assigned to the control (n = 6) or exercised (6) groups. Horses in the exercised group ran on a high-speed treadmill 5 d/wk for 6 months. Horses in the control group were hand walked for the sam e amount of time. Results of clinical, radiographic, nuclear scintigraphic, and computed tomographic examinations, and serum and synovial concentratio ns of biochemical markers of bone metabolism were compared between groups. Results-Exercised horses were significantly lamer at the end of the study t han control horses. Radionuclide uptake in the metacarpal condyles, but not in the carpal joints, was greater in exercised horses, compared with contr ol horses. Exercised horses also had a higher subchondral hone density in t he metacarpal condyles than control horses, but such differences were not d etected in the carpal bones. Conclusions and Clinical Relevance-None of the diagnostic techniques evalua ted was sufficiently sensitive to detect all osteochondral damage. Computed tomography and computed tomographic osteoabsorptiometry were superior to c onventional radiography for detecting small osteochondral fragments. Nuclea r scintigraphy was a sensitive indicator of subchondral bone change but lac ked specificity for describing lesions and discerning normal bone remodelin g from damage. Newer techniques such as computed tomography may help clinic ians better diagnose early and subtle joint lesions in horses prior to deve lopment of gross joint damage.