Human Movement Science & Functional Anatomy of the:

Semitendinosus and Semimembranosus

by Brent Brookbush MS, PES, CES, CSCS, ACSM H/FS

By Any Other Name:

  • These muscles are often referred to as the "medial hamstrings", in opposition to the "lateral hamstrings (a.k.a.the biceps femoris)".  They are often abbreviated the "Semi's".

Note: the semitendinosus and semimembranosus, the continuation into the sacrotuberous ligament, and the innervation via the tibial branch of the sciatic nerve.



  • Origin: Tuberosity of ischium by tendon common with with the long head of the biceps femoris (11).
  • Insertion: Proximal part of the medial surface of the tibia and deep crural fascia.  The tendon of the semitendinosus contributes the distal fibers of the pes anserinus tendon - a tendon that is comprised of the distal tendons of the semitendinosus, gracilis and sartorius (11,16).

    • The semitendinosus is a superficial muscle of the posterior thigh, bordered by the long head of the biceps femoris laterally, and the semimembranosus medially (along with portions of the adductor magnus).  All of the hamstring muscles (including the biceps femoris) lay in the posterior compartment of the thigh, with the semitendinosus bordered anteromedially by the posteromedial intermuscular septum.

        • The semitendinosus can be palpated with relative ease by locating the space between the two large bands that comprise the hamstring tendons just superior to the posterior knee.  As you course your fingers up the "valley" created by the division in the hamstrings.  You can feel musculotendinous junction invest into the long cylindrical