Biceps Femoris Anatomy - Everything You Need To Know - Dr. Nabil Ebraheim

Video Description

Dr. Ebraheim’s educational animated video describes the condition of biceps femoris muscle anatomy.

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Biceps Femoris Anatomy
The biceps femoris is a muscle of the posterior thigh. The biceps femoris is one of the three flexor muscles of the posterior thigh. The ischial tuberosity is divided by a transverse ridge into an upper quadrangular portion and a lower triangular portion and each portion is divided into medial and lateral parts. The biceps femoris has two heads of origin. The long head of the biceps femoris arises from the upper and medial part on the back of the ischial tuberosity. The short head of the biceps femoris arises from the lateral lip of the linea aspera on the posterior femur. Both heads of the biceps femoris are inserted into the head of the fibula along with the lateral collateral ligament and the popliteofibular ligament. The insertion of the structure from anterior to posterior on the fibular head: lateral collateral ligament, popliteofibular ligament, and biceps femoris tendon. The biceps femoris tendon is the most posterior structure on the proximal fibula. The upper medial portion of the ischial tuberosity is where the insertion of the biceps femoris and semitendinosus is located. Muscle strains or tears of the muscle can occur in sports that require rapid acceleration and deceleration. Eccentric loading of the muscle and the tendon may cause these injuries. Injury usually involves the myotendinous junction approximately 12cm distal to the ischium. Complete rupture or avulsion from the ischial tuberosity may also occur. This complete rupture usually needs repair. If not repaired, the rupture will lead to significant functional impairment which is more profound during vigorous activity. High sciatic nerve lesions can mimic peroneal neuropathy at the fibular head. The patient in both conditions will have foot drop, so we don’t know if the lesion occurs from the common peroneal nerve at the knee level or if it occurs at a higher level from a high sciatic nerve injury. Both patients have foot drop. When we do EMG, if we find that there is EMG abnormalities in the short head of the biceps femoris muscle, then this injury is a high sciatic nerve injury. But if we find that the short head of the biceps has no EMG changes, then the lesion occurs from injury to the common peroneal nerve at the fibular head and the lesion is not to the sciatic nerve. The long head is innervated by the tibial branch of the sciatic nerve (L5, S2). The short head of the biceps femoris is innervated by the common peroneal branch of the sciatic nerve (L5, S2). The sciatic nerve starts in the lower back and runs through the buttock and lower limb. In the thigh, the tibial part innervates the long head of the biceps femoris muscle while the peroneal part innervates the short head. The tendon of biceps femoris muscle forms the lateral hamstring. The biceps femoris muscle vascular supply is derived from the perforating branches of the inferior gluteal artery, the profunda femoris artery, and the popliteal artery. At this level, the sciatic nerve travels down the thigh to the area of the popliteal fossa and at this point it divides into the tibial and common peroneal nerves. The biceps femoris muscle flexes the knee joint and laterally rotates the knee joint when the knee is flexed. The biceps femoris also extends the hip joint (long head only).