Overview
It covers most of the medial thigh, caudal to the sartorius. The gracilis muscles of both sides arise together on the pelvic symphysis through the symphyseal tendon. Its cranial border and the sartorius bound the femoral triangle, through which the femoral vessels pass.
Origin
Pelvic symphysis, through the symphyseal tendon.
Insertion
Medial surface of the proximal tibia and medial patellar ligament, through an aponeurosis continuous with the crural fascia.
Action
Adducts the pelvic limb, extends the hip and flexes the stifle.
Innervation
Obturator nerve (n. obturatorius).
Clinical relevance
- Fibrotic myopathy, which mainly affects the semitendinosus, can extend to the gracilis and semimembranosus: muscle tissue is replaced by fibrous tissue and the swing phase of the stride ends with an abrupt slap of the hoof on the ground.
- Obturator nerve paralysis can occur in mares after dystocia, from compression of the nerve against the pelvis. Without the adductors, the limb slides laterally when it bears weight.