Biceps Femoris Muscle is the most lateral component of the so-called hamstring muscles. Classically, this muscle’s insertion into the head of the fibula has been described but further details of its anatomy have not been universally appreciated. Additional insertions into the crural fascia and tibia have been described. We dissected 56 cadavers paying especially close attention to the insertion of the biceps femoris muscle. The tendon of this muscle was found to have both medial and lateral slips each with an anterior and posterior component. The biceps femoris (also biceps femoris muscle, Latin musculus biceps femoris) is a two-headed muscle of the lower limb located in the posterior region of the thigh. The biceps femoris has two portions – the long head and the short head.
The biceps femoris is one of the hamstring muscles at the back of the thigh. It originates in two places: the ischium (lower, the rear portion of the pelvis, or hipbone) and the back of the femur (thighbone). The fibers of these two origins join and are attached at the head of the fibula and tibia, the bones of the lower leg. This muscle extends the thigh, rotates it outward, and flexes the leg at the knee.
Origin of Biceps Femoris Muscle
It has two heads of origin:
- The long head – arises from the lower and inner impression on the posterior part of the tuberosity of the ischium. This is a common tendon origin with the semitendinosus muscle, and from the lower part of the sacrotuberous ligament.
- 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.[rx]
Insertion
- Inferiorly, the aponeurosis condenses to form a tendon which predominantly inserts onto the lateral side of the head of the fibula. There is a second small insertional attachment by a small tendon slip into the lateral condyle of the tibia.[rx]
- At its insertion, the tendon divides into two portions, which embrace the fibular collateral ligament of the knee joint. Together, this joining of tendons is commonly referred to as the conjoined tendon of the knee.[rx][rx]
Arterial Supply
The muscle’s vascular supply is derived from the anastomoses of several arteries: the perforating branches of the profundal femoris artery, the inferior gluteal artery, and the popliteal artery.[rx]
- Inferior gluteal artery
- Perforating arteries
- Popliteal artery
Nerve Supply
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 a common fibular branch of the sciatic nerve (L5, S1), while the long head is innervated by the tibial branch of the sciatic nerve (L5, S1).[rx]
- Long head – a tibial division of the sciatic nerve (L5-S2)
- Short head – a common peroneal division of the sciatic nerve
or
- Long head – tibial nerve
- Short head – common peroneal nerve
Function of Biceps Femoris Muscle
- Flexes knee joint
- Laterally rotates knee joint (when the knee is flexed)
- Extends hip joint (long head only)
- External rotation of the thigh (long head only)
- Long head – flexes the knee, extends hip, laterally rotates lower leg when knee slightly flexed, assists in lateral rotation of the thigh when hip extended
- Short head – flexes the knee, laterally rotates lower leg when knee slightly flexed
Functional contributions
- Through a reversed origin insertion action, the long head gives posterior stability to the pelvis
- Both heads provide rotary stability by preventing forward dislocation of the tibia on the femur during flexion
- Its contributions to the arcuate ligament complex at the posterolateral corner of the knee also provide varus and rotatory stability to the knee.