Quadriceps femoris muscle

The quadriceps femoris muscle (, also called the quadriceps extensor, quadriceps or quads) is a large muscle group that includes the four prevailing muscles on the front of the thigh. It is the sole extensor muscle of the knee, forming a large fleshy mass which covers the front and sides of the femur. The name derives .

Structure

Parts

The quadriceps femoris muscle is subdivided into four separate muscles (the 'heads'), with the first superficial to the other three over the femur (from the trochanters to the condyles):
*The rectus femoris muscle occupies the middle of the thigh, covering most of the other three quadriceps muscles. It originates on the ilium. It is named for its straight course.
*The vastus lateralis muscle is on the ''lateral side'' of the femur (i.e. on the outer side of the thigh).
*The vastus medialis muscle is on the ''medial side'' of the femur (i.e. on the inner part thigh).
*The vastus intermedius muscle lies between vastus lateralis and vastus medialis on the ''front'' of the femur (i.e. on the top or front of the thigh), but deep to the rectus femoris muscle. Typically, it cannot be seen without dissection of the rectus femoris.

Attachments

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.

Other muscles

There is a small fifth muscle of the quadriceps complex — the articularis genus muscle — that is not often included.

In addition, cadaver studies have confirmed the presence of a sixth muscle, the tensor vastus intermedius. While this muscle has a variable presentation, 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 muscle, 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.

Innervation

The quadriceps femoris is innervated by the femoral nerve, which originates from L2, L3, L4.

Function

All four quadriceps are powerful extensors 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.Therapeutic Exercises, Carolyn Kisner & Lynn A. Colby, 5th ed. (2002) 692-93.

Clinical significance

The quadriceps femoris muscle is a target for manual therapy and physical therapy from repetitive strain injuries, such as from skiing.

The quadriceps femoris muscle is the most common site of myositis ossificans.

Society and culture

Training

In strength training, the quadriceps are trained by several leg exercises including the squat, leg press, and leg extension.

Etymology

The proper Latin plural form of the adjective ''quadri'' would be ''quadricipites''. In modern English usage, ''quadriceps'' is used in both the singular and plural form. The singular form ''quadricep'', produced by back-formation, is frequently used.

Additional images

File:Knee diagram.svg, The quadriceps tendon connects to the top part of the kneecap (patella)
File:Gray432 color.png, Cross-section through the middle of the thigh
File:Gray1238.png, The quadriceps forms the bulk of front part of the thigh

See also

* Hamstring
* Gluteal muscles

References

External links

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Knee extensors
Thigh muscles
Anterior compartment of thigh
Muscles of the lower limb