Other than fractures or other trauma, common causes of lameness in the carpus include carpal hyperextension injury and flexural carpal deformity.
Carpal Hyperextension Injury
Carpal hyperextension injury occurs with jumping down from a distance and damaging the palmar fibrocartilage and intercarpal ligaments. This is not damage to the flexor tendons. Mild injuries may be managed with prolonged splinting, but generally surgery is the treatment of choice, especially in larger dogs with significant hyperextension. Surgery involves surgical fusion of the affected joints by removing the articular cartilage, packing the area with bone graft, and stabilizing the area with a bone plate and screws. The area is usually protected with a cast or splint until there is some bony healing. If possible, a partial arthrodesis may be performed of the lower joints, with preservation of the main motion joint. However, if that joint is also involved, a complete fusion must be performed which eliminates any motion of the carpus. Dogs usually adapt quite well, however.
Carpal Flexural Deformity
Carpal flexural deformity is a condition seen in young dogs. The flexor carpi ulnaris muscle appears to be very tight, resulting in the carpus being in a flexed position during weight bearing, with some rotation of the foot. Generally change to a large breed growth diet and time result in correction, but occasionally surgery is necessary.