CorpusHuman Anatomy
MuscularMuscle

Biceps femoris

Musculus biceps femoris

Also known as: lateral hamstring

The lateral hamstring, with a long head from the ischial tuberosity and a short head from the femur. It inserts on the head of the fibula, extends the hip (long head), flexes the knee and laterally rotates the flexed leg.

Show on body map Muscles — Posterior View

Overview

The long head arises from the medial facet of the ischial tuberosity by a common tendon with semitendinosus, and from the sacrotuberous ligament. The short head arises from the lateral lip of the linea aspera and the lateral supracondylar line. The two heads join into a tendon that forms the lateral border of the popliteal fossa and inserts on the head of the fibula, where it is split by the fibular collateral ligament. The common fibular nerve follows its medial border, then winds superficially around the neck of the fibula, where it is vulnerable.

It flexes the knee and is the only lateral rotator of the flexed knee. The long head also extends the hip. The two heads have separate nerves: the long head is supplied by the tibial division and the short head by the common fibular division of the sciatic nerve.

Parts & subdivisions

  1. Long head
    Ischial tuberosity. Tibial division. Crosses the hip and knee.
  2. Short head
    Linea aspera. Common fibular division. Crosses the knee only.

Anatomy

Origin

Long head: ischial tuberosity (and sacrotuberous ligament). Short head: lateral lip of the linea aspera and the lateral supracondylar line.

Insertion

Lateral side of the head of the fibula (and the lateral tibial condyle).

Action

Flexion of the knee; lateral rotation of the flexed knee; extension of the hip (long head).

Innervation

Long head: tibial division of the sciatic nerve. Short head: common fibular division.

Nerve roots

L5–S2

Arterial supply

Perforating branches of the profunda femoris; inferior gluteal artery; superior lateral genicular artery.

Relations

Forms the superolateral border of the popliteal fossa. The common fibular nerve runs along its medial edge.

Function

  • Flexes the knee and laterally rotates the flexed leg
  • Extends the hip (long head)

Clinical significance

Common fibular nerve injury

The nerve lies just medial to the biceps tendon and then winds around the fibular neck. Fibular neck fractures, tight casts or crossing the legs can injure it, causing foot drop, a steppage gait and loss of eversion.

Compiled from standard anatomy and physiology references — see the Muscular System sources. For education only; not medical advice.