Clinical, radiographic, and scintigraphic findings associated with enthesitis of the lateral collateral ligaments of the tarsocrural joint in standardbred racehorses.

Injury of the lateral collateral ligaments of the tarsocrural joints was diagnosed in nine Standardbred pacers. The average age was 4.9 years. The severity of the lameness varied from severe to subtle and joint effusion was seen in eight of 10 tarsocrural joints. A positive hindlimb flexion test was seen in four of six cases in which results were recorded. The identification of the site of involvement was based on a focal intense 'hot spot' seen on scintigraphy, and new bone formation seen radiographically at the anatomical sites of insertion of the long lateral collateral ligament of the tarsocrural joint in nine limbs and the short lateral collateral ligament of one limb. The authors believe this injury to be enthesitis caused by the cyclic trauma of training and racing speed. The primary therapy was rest. Of six cases which returned to training, three raced as well or better than before injury.