Semimembranosus
| Pronuncation | sem-ee-mem-bran-OH-sus |
| Derivation | Half- (semi) membrane. |
| Origin | Ischial tuberosity. |
| Insertion | Medial condyle of the tibia. |
| Action | Pulls the thigh backwards, bends the leg at the knee, and rotates the lower leg inward. |
Semimembranosus lies under semitendinosus, and can be seen on either side. Its medial bulk is framed by gracilis, adductor magnus, and semitendinosus. It can be seen as lying in the same column, as it were, as adductor magnus.
Its lateral side appears as a short, curved bulge added to the lower end of semitendinosus only slightly to the outside.
Its tendon joins the group of tendons running to the medial condyle of the tibia, and contributes to its form.