Origin

Biceps Femoris:

  • Long head—ischial tuberosity, sacrotuberous ligament
  • Short head—linea aspera, lateral supracondylar ridge, lateral intermuscular septum

Semitendinosus: Ischial tuberosity
Semimembranosus: Ischial tuberosity

Insertion

Biceps Femoris: Lateral side of head of fibula and lateral condyle of tibia
Semitendinosus: Medial surface of shaft of tibia
Semimembranosus: Medial surface of shaft of tibia

Actions

Biceps Femoris: Flexes leg, long head also extends thigh
Semitendinosus: Flexes and slightly medially rotates leg; after flexion, extends thigh
Semimembranosus: Flexes and slightly medially rotates leg; after flexion, extends thigh

Nerve

Biceps Femoris

  • Long head—tibial part of sciatic nerve (S1–S3)
  • Short head—common peroneal part of sciatic nerve (L5, S1, S2)

Semitendinosus: Tibial portion of sciatic nerve (L5, S1, S2)
Semimembranosus: Tibial portion of sciatic nerve (L5, S1, S2)

Note

During walking or running, the hamstrings are used to slow down the leg at the end of its swing and prevent the trunk from flexing at the hip. They are susceptible to being strained by resisting the momentum of these body parts.