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Portrait of Biceps femoris

Anatomy · Muscles

Biceps femoris

The lateral hamstring

Lower limb · thigh, posterior compartment

Biceps femoris is the two-headed muscle on the outer side of the back of the thigh, the lateral hamstring. Its long head arises from the ischial tuberosity and its short head from the linea aspera; both insert on the head of the fibula. It flexes the knee and, through the long head, extends the hip; its two heads have different nerve supplies.

How to spot them

  • ▸Lateral of the three hamstring muscles, passing down the outer back of the thigh
  • ▸Long head from the ischial tuberosity, short head from the shaft of the femur
  • ▸Tendon is the one you feel on the outer side behind the knee
  • ▸The common fibular nerve runs along its medial border to the fibular neck

What to know

The hamstring muscle with a short head arising from the femoral shaft, unlike its two neighbours

Biceps femoris.

The tendon felt on the outer side of the popliteal fossa, behind the knee

Biceps femoris — the lateral hamstring tendon.

A muscle whose long head is supplied by the tibial division of the sciatic nerve and whose short head by the common fibular division

Biceps femoris — the only muscle with two nerves in the posterior thigh.

It inserts mainly on the head of the fibula

Biceps femoris.

A muscle whose tendon the common fibular nerve follows down to the neck of the fibula

Biceps femoris.

It shares an origin from the ischial tuberosity with semitendinosus

Biceps femoris — the long head.

Key ideas

  • Its long head crosses two joints and is the hamstring most often strained in sprinting.
  • The common fibular nerve runs along its tendon and is vulnerable at the fibular neck, where injury causes foot drop.

Quick-fire facts

  • •Origin: long head from the ischial tuberosity (common tendon with semitendinosus); short head from the lateral lip of the linea aspera and the supracondylar ridge.
  • •Insertion: lateral aspect of the head of the fibula.
  • •Nerve supply: long head by the tibial division of the sciatic nerve; short head by the common fibular division (L5–S2).
  • •Actions: flexes the knee, laterally rotates the flexed knee; the long head also extends the hip.
  • •It is the only hamstring with two heads and the only one that attaches to the fibula.
  • •It forms the superolateral border of the popliteal fossa.
  • •Biceps femoris means 'two-headed muscle of the thigh'.

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Sources