|Quadriceps femoris muscle|
|Origin||Combined rectus femoris and vastus muscles|
|Actions||Knee extension; Hip flexion (Rectus femoris only)|
|Latin||Musculus quadriceps femoris|
|Anatomical terms of muscle|
It is subdivided into four separate muscles (the 'heads'):
- 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 (i.e. on the outer side of the thigh).
- Vastus medialis is on the medial side of the femur (i.e. on the inner part thigh).
- Vastus intermedius 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. 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.
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.
Femoral nerve (L2, L3, L4).
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.
Society and culture
In strength training, the quadriceps are trained by several leg exercises. Effective exercises include the squat and leg press. The isolation movement (i.e. targeting solely the quadriceps) is the leg extension.
The proper Latin plural form of the adjective quadriceps would be quadricipites. In modern English usage, quadriceps is used in both singular and plural. The singular form quadricep, produced by back-formation, is frequently used.
The quadriceps tendon connects to the top part of the kneecap (patella)
- Grob, K; Ackland, T; Kuster, MS; Manestar, M; Filgueira, L (6 January 2016). "A newly discovered muscle: The tensor of the vastus intermedius" (PDF). Clinical Anatomy. 29 (2): 256–263. doi:10.1002/ca.22680. PMID 26732825. S2CID 38157592.
- Therapeutic Exercises, Carolyn Kisner & Lynn A. Colby, 5th ed. (2002) 692-93.
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