Biceps Femoris Muscle

Written By: Chloe Wilson, BSc(Hons) Physiotherapy
Reviewed by: KPE Medical Review Board

Biceps Femoris is one of the three hamstring muscles found on the back of the thigh.

Its name means:

• Biceps: 2 headed muscle
• Femoris: at the femur (thigh bone)

The two heads of biceps femoris originate quite far apart from each other - he "long head" arises from the pelvis, and the "short head" arises from the femur.

The muscle runs centrally down the back of the thigh to the knee and helps the other hamstring muscles to bend the knee.

Origin & Insertion

The long head of biceps femoris originates with the semitendinosus tendon, from the lower medial facet of the ischial tuberosity and the sacrotuberous ligament.

The two tendons descend together for a short distance before dividing into two individual muscles.

The long head of biceps femoris forms a fusiform muscle – a spindle shape with the muscle belly being wider than the origin and insertion.

It runs downwards and laterally (from the inner to outer side of the leg) across the back of the thigh, on top of the sciatic nerve. As it nears the knee it narrows and is joined underneath by the short head of biceps.

The short head of biceps femoris attaches to the lower half of the lateral lip of the linea aspera, just below the insertion of gluteus maximus, and extends down onto the upper half of the supracondylar line of the femur, with some fibres arising from the intermuscular septum.

It runs underneath the long head of biceps and the two parts of the muscle join forming one tendon in the distal thigh.

Having joined together, just before its attachment to the fibular head, the biceps femoris tendon splits into three.

1. Some fibres join to the fibular/lateral collateral ligament
2. Some attach on to the lateral tibial condyle 
3. The rest attach to the back of the lateral intermuscular septum. 

Summary

Muscle Group: Biceps Femoris is one of the three hamstrings muscles on the back of the thigh

Action: Knee flexion, knee rotation, hip extension

Origin: Two heads – long head from the lower medial facet on the ischial tuberosity, the short head from the lower half of the lateral lip of the linea aspera

Insertion: Head of fibula, fibula collateral ligament, lateral tibial condyle and lateral intermuscular septum

Nerve Supply: Long Head – tibial branch of the sciatic nerve. Short Head – common peroneal nerve (both L5, S1, S2)

Special Functions: Straightening the back from a bent position, controls the pelvis in standing, controls the knee as it swings forwards when walking