The gastrocnemius muscle and associated tendon are critical for rising and weight bearing. The function of the gastrocnemius muscle is to extend the hock and flex the stifle. It is part of the caudal muscles of the crus. It is innervated by the Tibial nerve and inserts proximally on supracondylar tuberosities (medial and lateral) of the femur. Distally, it becomes part of the common calcaneal tendon on the calcanean tuber (point of the hock).
Rupture is most commonly observed in foals and juvenile horses. As mentioned above the gastrocnemius muscle is a critical part of the reciprocal apparatus of the hindlimb. In newborn foals it can occur as a consequence to a dystocia, particularly a hip lock dystocia. Tearing usually occurs at the musculotendinous junction. The prognosis for athletic soundness in foals is guarded to poor when the tear is moderate to severe. Some form of cast or splint is required. Injury to the gastrocnemius muscle is rare in adult horses, where it carries a poor prognosis for a return to soundness.
The diagnosis can be confirmed by demonstrating hyperflexion of the hock when standing, or when recumbent in a foal (see image below). Normally when the hock is flexed the stifle will flex. The femoral artery and vein are positioned caudally in the crus in association with the gastrocnemius muscle and can be disrupted.
Tags: Musculoskeletal; Foals