Biceps femoris muscle

The biceps femoris muscle (or biceps femoris ) is an external muscle on the posterolateral thigh. It is part of the posterior compartment made up of three muscles called the hamstring muscles: 1) biceps femoris, 2) semitendinosus, 3) semimembranosus. Except for the short head or portion of the biceps, the hamstrings cross the hip and knee joints. The biceps femoris muscle is the superolateral limit of the popliteal fossa.

Path

As its name indicates, it results from the fusion –from below– of two differentiated muscular bodies:

• Portion or long or ischiatic head: They originate in the ischiatic tuberosity of the ischion together the semi-tendinous in the so-called joint tendon.
• Short or femoral portion or head: They originate in the lower third of the intersection, from the lateral lip of the rough line of the femur.

In its course, the muscle belly of the long head crosses the posterior thigh obliquely from medial to lateral and joins the short head distally. Together, the fibers from the two heads form a tendon, which is palpable on the lateral aspect of the distal thigh.

Both muscular bodies end in a common tendon that attaches to:

1. In the styling process of the Peron.
2. External tuberosity of warmth.
3. Tibial aponeurosis.

The main part of the tendon inserts on the lateral surface of the fibular head, extensions of the tendon fusing with the fibular collateral ligament and with associated ligaments on the lateral aspect of the knee joint. At insertion, the upper edge corresponds to the head, the fibula itself, and may also contain tendinous expansions to the lateral condyle of the tibia.

Actions

Its function is twofold:

1. Flexor of the leg on the thigh, while rotating to that outward – main action.
2. The long portion spreads the thigh over the pelvis. It also rotates the hip in the lateral sense.

Innervation

It belongs to the neuromuscular system of the greater sciatic nerve. The long head or head is innervated by the tibial division of the sciatic nerve and the short head is innervated by the peroneal division of the same nerve.

Irrigation

It is supplied proximally by the inferior gluteal artery. The lower portion does so through the popliteal artery. In its course it may be supplied by the perforating branches of the deep femoral artery.