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Quadriceps femoris muscle

Synonym: quadriceps muscle of the thigh, four-headed thigh extensor, quadriceps
German: Musculus quadriceps femoris

1 Definition

The quadriceps femoris muscle is located on the ventral side of the thigh and consists of four parts: the rectus femoris muscle, the vastus intermedius muscle, the vastus medialis muscle, and the vastus lateralis muscle.

2 Devolution

2.1 Rectus femoris muscle

from Latin: rectus - upright, erect

The rectus femoris muscle has two muscle heads. Its Caput rectum (upright head) has its origin at the anterior lower iliac spine, the spina iliaca anterior inferior. The Caput reflexum (flected head), which is highly variable, has its origin on the upper border of the socket of the hip joint (acetabulum). The tendon of the muscle sets out around ten centimeters cranial to the patella. Since this muscle part is two-hinged , it also effects a flexion in the hip joint alongside the extension in the knee joint.

2.2 Vastus intermedius muscle

from Latin: vastus - wide

The vastus intermedius muscle has its origin in the frontal and lateral surfaces of the upper two thirds of the thigh bone. Around the middle of the bone, the muscle fibers progressively transforms into a tendon. Usually, this muscle part is completely covered by the rectus femoris muscle.

2.3 Vastus lateralis muscle

The vastus lateralis muscle usually has the biggest muscle mass among the four heads of the quadriceps. Essentially, it has its origin in a broad aponeurosis that is fixed to the cranial part of the intertrochanteric line, the greater trochanter and the linea aspera of the thigh bone. A smaller part of the fibers has its origin in the lateral intermuscular septum of the femur.

2.4 Vastus medialis muscle

The vastus medialis muscle has its origin on the medial side of the femur, and its lower part at the intertrochanteric line. The origin follows the medial lip of the linea aspera into caudal direction until the medial supracondylar line.

The common tendon of the four muscle parts inserts on the superior pole of the patella. Some fibers pass over the patella and thereby enclose it as a sesamoid bone. The muscular strength is transmitted via the patellar ligament that inserts into the tibial tuberosity.

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3 Innervation

The innervation is provided by the femoral nerve (segments L2-L4) from the lumbar plexus.

4 Function

The quadriceps femoris muscle is the only extensor of the knee, which is why itís of utmost importance for the straightening up of the body (eg. from squatting). Since it works against gravity, it clearly surpasses the strength of the thigh flexors. The rectus femoris muscle also can bend in the hip joint, however, its effect is relatively weak. The muscle is only able to perform its full extension in the knee when the hip joint is extended, since the rectus femoris muscle becomes inefficient in a bent hip.

The four muscles are also responsible for the patella to remain in its sliding groove. When they are unevenly developed, the patella can suffer a luxation.

Specialties: Anatomy

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