The semitendinosus has an exceptionally long thin tendon (relative to its belly) making it ideal for tendon graft harvest. It is one of the components of the pes anserinus, along with gracilis and sartorius.
| Origin | Ischial tuberosity — medial facet, shared with the long head of biceps femoris |
|---|---|
| Insertion | Superomedial tibia — pes anserinus (along with gracilis and sartorius) |
| Nerve Supply | Tibial nerve (L5, S1, S2) |
| Blood Supply | Perforating branches of the profunda femoris |
| Actions | Flexes the knee — the most superficial medial hamstring; Extends the hip; Medially rotates the tibia when the knee is flexed; Contributes to pes anserinus tendon complex stability |
|---|
The semitendinosus tendon (with gracilis) is the most commonly harvested graft for ACL reconstruction (quadrupled hamstring graft — 4-strand STSG). The long tendon allows harvesting with a tendon stripper. After harvest, the semitendinosus regenerates a new tendon over 12-24 months from the remaining muscle belly.
Palpated as the prominent posteromedial knee tendon at the medial hamstring — the most palpable of the three hamstring insertions.
Semitendinosus tendon harvesting (with gracilis) for quadrupled hamstring ACL graft, with the tendon regenerating over 12-24 months post-harvest.
