Biceps femoris muscle
|Lateral aspect of right leg. Biceps femoris muscle long head labeled|
|Same picture with the visible part of the short head beneath the long head labeled|
|Latin||musculus biceps femoris|
|Gray's||subject #128 478|
|Origin||tuberosity of the ischium, linea aspera, femur|
|Insertion||the head of the fibula which articulates with the back of the lateral tibial condyle|
|Artery||inferior gluteal artery, perforating arteries, popliteal artery|
|Nerve||long head: tibial nerve
short head: common peroneal nerve
|Actions||flexes knee joint, laterally rotates knee joint (when knee is flexed), extends hip joint (long head only)|
Origin and insertion 
It has two heads of origin;
- one, the long head, arises from the lower and inner impression on the back part of the tuberosity of the ischium, by a tendon common to it and the semitendinosus, and from the lower part of the sacrotuberous ligament;
- the other, the short head, arises from the lateral lip of the linea aspera, between the adductor magnus and vastus lateralis, extending up almost as high as the insertion of the gluteus maximus; from the lateral prolongation of the linea aspera to within 5 cm. of the lateral condyle; and from the lateral intermuscular septum.
The fibers of the long head form a fusiform belly, which passes obliquely downward and lateralward across the sciatic nerve to end in an aponeurosis which covers the posterior surface of the muscle, and receives the fibers of the short head; this aponeurosis becomes gradually contracted into a tendon, which is inserted into the lateral side of the head of the fibula, and by a small slip into the lateral condyle of the tibia.
From the posterior border of the tendon a thin expansion is given off to the fascia of the leg. The tendon of insertion of this muscle forms the lateral hamstring; the common fibular (peroneal) nerve descends along its medial border.
Both heads of the biceps femoris perform knee flexion.
Since the long head originates in the pelvis it is also involved in hip extension. The long head of the biceps femoris is a weaker knee flexor when the hip is extended (because of active insufficiency). For the same reason the long head is a weaker hip extender when the knee is flexed.
When the knee is semi-flexed, the biceps femoris in consequence of its oblique direction rotates the leg slightly outward.
The short head of the biceps femoris develops in the flexor compartment of the thigh and is thus innervated by common peroneal branch of the sciatic nerve (L5, S2), while the long head is innervated by the tibial branch of the sciatic nerve (L5, S2).
Blood supply 
See also 
Additional images 
Further reading 
- Kumakura, Hiroo (July 1989). "Functional analysis of the biceps femoris muscle during locomotor behavior in some primates". American Journal of Physical Anthropology 79 (3): 379–391. doi:10.1002/ajpa.1330790314. PMID 2504047.
- Marshall, John L.; Girgis, Fakhry G.; Zelko, Russel R. (1972). "The Biceps Femoris Tendon and Its Functional Significance (PDF)". J Bone Joint Surg Am. 54 (54): 1444–1450.
- Sneath, R. S. (1955 October). "The insertion of the biceps femoris". J Anat. 89 (89(Pt 4)): 550–553. PMC 1244747. PMID 13278305.