The quadriceps femoris is a large muscle group that includes the four prevailing muscles on the front of the thigh. It is the great extensor muscle of the knee, forming a large fleshy mass which covers the front and sides of the femur. The name derives.
Structure
It is subdivided into four separate muscles :
Rectus femoris occupies the middle of the thigh, covering most of the other three quadriceps muscles. It originates on the ilium. It is named from its straight course.
The other three lie deep to rectus femoris and originate from the body of the femur, which they cover from the trochanters to the condyles:
*Vastus lateralis is on the lateral side of the femur.
*Vastus medialis is on the medial side of the femur.
*Vastus intermedius lies between vastus lateralis and vastus medialis on the front of the femur, but deep to the rectus femoris. Typically, it cannot be seen without dissection of the rectus femoris.
The rectus femoris arises from the anterior inferior iliac spine and from the superior edge of the acetabulum. It is thus a biarticular muscle. The other parts of the quadriceps arise from the surface of the femur. All four parts of the quadriceps muscle ultimately insert into the tuberosity of the tibia via the patella, where the quadriceps tendon becomes the patellar ligament. There is a small fifth muscle of the quadriceps complex called the articularis genus that is not often included. In addition, cadaver studies have confirmed the presence of a sixth muscle, the tensor vastus intermedius. While the muscle has variable presentations, it consistently originates at the proximal femur, runs between the vastus lateralis and vastus intermedius muscles, and inserts distally at the medial aspect of the patellar base. Historically considered a part of the vastus lateralis, the tensor vastus intermedius muscle is innervated by an independent branch of the femoral nerve and its tendinous belly can be separated from the vasti lateralis and intermedius muscles in most cases.
Nerve supply
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Function
All four quadriceps are powerfulextensors of the knee joint. They are crucial in walking, running, jumping and squatting. Because the rectus femoris attaches to the ilium, it is also a flexor of the hip. This action is also crucial to walking or running as it swings the leg forward into the ensuing step. The quadriceps, specifically the vastus medialis, play the important role of stabilizing the patella and the knee joint during gait.
