Rupture of the gastrocnemius muscle or tendon is relatively rare. It is most likely to be associated with deficiencies of calcium, phosphorus, and vitamin D. Prolonged recumbency, with resulting myositis and struggling to rise, occasionally precipitates rupture of these muscles. Occasionally, the condition has been associated with pyelonephritis, which presumably causes a myositis, weakening the muscle enough to permit rupture. Injections of irritating medicaments into the gastrocnemius muscle may cause necrosis and rupture.
The hock remains flexed. When the muscle is completely ruptured, the standing animal rests the hock and distal portion of the limb on the ground or walking surface, which is diagnostic, although rupture of the Achilles tendon may produce an identical gait.
Successful treatment is extremely unlikely in heavy adult animals. A leg cast or splint that maintains the hock in extension, supplying adequate vitamins and minerals, and proper nursing may be successful, but a long recovery period is required.
