Musculus biceps femoris
The biceps femoris is one of the large muscles in the posterior compartment of the thigh and a component of the hamstrings. It has a long and a short head, each with different functions and innervation.
Its medial border forms the superolateral border of the popliteal fossa.
- long head: medial facet of the ischial tuberosity
- short head: lateral linea aspera and lateral supracondylar line of the femur and adjacent intermuscular septum
- insertion: fibular head, crural fascia and lateral tibial condyle
- flexes knee joint
- laterally rotates knee joint (when the knee is flexed)
- extends hip joint (long head only)
- external rotation of the thigh (long head only)
- arterial supply
- antagonist: quadriceps
- absence of the short head
- exclusive tibial insertion (rare)