Short head of biceps femoris

At a glance

English

Short head of biceps femoris

Latin (TA2)

Caput breve musculi bicipitis femoris

System

Muscle

Region

Lower limb

Side

Paired, left and right

About the short head of biceps femoris

Biceps femoris has two heads, and the short head is the one that arises from the femur rather than the pelvis. It therefore crosses only the knee and is not counted as a true hamstring, although it works closely with them. It lies deep to the long head on the lateral side of the back of the thigh, filling the lower part of the space between the adductors and the vastus lateralis.

Its origin is the outer lip of the linea aspera, from a level close to the lower edge of the gluteus maximus insertion down along the lateral supracondylar line almost to the lateral condyle. It also takes fibres from the lateral intermuscular septum that separates it from vastus lateralis. Its fibres pass down and slightly outwards to join the deep surface of the aponeurosis of the long head. The resulting single tendon splits around the fibular collateral ligament and attaches to the head of the fibula, with a slip to the lateral tibial condyle.

Because it acts only on the knee, the short head is a pure knee flexor whose power does not depend on the position of the hip. With the knee partly bent it also turns the leg outwards, the only strong lateral rotator of the flexed knee. This independence from the hip is useful in late swing in running, when it helps slow the forward travel of the leg.

Its nerve is distinct from the rest of the hamstrings: it is supplied by the common fibular division of the sciatic nerve, a sign that it develops with the extensor-side muscles. Its blood comes from the perforating branches of the deep femoral artery and from the superior lateral genicular branch of the popliteal artery. The short head is sometimes absent, and it is a less frequent site of strains than the long head.

Attachments, action and supply

Origin

Outer lip of the linea aspera, upper lateral supracondylar line of the femur and the lateral intermuscular septum.

Insertion

Head of the fibula through the common biceps tendon, with a slip to the lateral condyle of the tibia.

Action

Flexes the knee and laterally rotates the leg when the knee is semi-flexed.

Nerve supply

Common fibular division of the sciatic nerve (L5, S1, S2).

Blood supply

Perforating branches of the deep femoral artery and the superior lateral genicular artery.