Biceps femoris muscle
Posterior view of right leg. Long head of muscle highlighted in red, short head labeled in the lower part of the image
|Latin||musculus biceps femoris|
|Origin||tuberosity of the ischium, linea aspera, femur|
|Insertion||the head of the fibula which articulates with the back of the lateral tibial condyle|
|deep femoral artery, perforating arteries|
|long head: tibial nerve
short head: common fibular nerve
|Actions||flexes knee joint, laterally rotates knee joint (when knee is flexed), extends hip joint (long head only)|
|Anatomical terms of muscle|
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.
The short head may be absent; additional heads may arise from the ischial tuberosity, the linea aspera, the medial supracondylar ridge of the femur, or from various other parts. The tendon of insertion may be attached to the Iliotibial band and to retinacular fibers of the lateral joint capsule.
It is a composite muscle as the short head of the biceps femoris develops in the flexor compartment of the thigh and is thus innervated by common fibular branch of the sciatic nerve (L5, S2), while the long head is innervated by the tibial branch of the sciatic nerve (L5, S2).
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.
|This section requires expansion. (November 2013)|
- 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. (October 1955). "The insertion of the biceps femoris". J Anat. 89 (89(Pt 4)): 550–553. PMC 1244747. PMID 13278305.
- UWash - long head
- UWash - short head
- Anatomy photo:14:06-0100 at the SUNY Downstate Medical Center
- Anatomy photo:14:st-0402 at the SUNY Downstate Medical Center