The quadriceps femoris muscle (, also called the quadriceps extensor, quadriceps or quads) is a large

muscle Skeletal muscles (commonly referred to as muscles) are Organ (biology), organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other ...

group that includes the four prevailing muscles on the front of the

thigh In human anatomy, the thigh is the area between the hip ( pelvis) and the knee. Anatomically, it is part of the lower limb. The single bone in the thigh is called the femur. This bone is very thick and strong (due to the high proportion of ...

. It is the sole extensor muscle of the knee, forming a large fleshy mass which covers the front and sides of the

femur The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates wit ...

. 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

(from the trochanters to the condyles): *The

rectus femoris muscle The rectus femoris muscle is one of the four quadriceps muscles of the human body. The others are the vastus medialis, the vastus intermedius (deep to the rectus femoris), and the vastus lateralis. All four parts of the quadriceps muscle atta ...

occupies the middle of the thigh, covering most of the other three quadriceps muscles. It originates on the

ilium Ilium or Ileum may refer to: Places and jurisdictions * Ilion (Asia Minor), former name of Troy * Ilium (Epirus), an ancient city in Epirus, Greece * Ilium, ancient name of Cestria (Epirus), an ancient city in Epirus, Greece * Ilium Building, a ...

. 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 The vastus medialis (vastus internus or teardrop muscle) is an extensor muscle located medially in the thigh that extends the knee. The vastus medialis is part of the quadriceps muscle group. Structure The vastus medialis is a muscle present ...

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 Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

and from the superior edge of the

acetabulum The acetabulum (), also called the cotyloid cavity, is a concave surface of the pelvis. The head of the femur meets with the pelvis at the acetabulum, forming the hip joint. Structure There are three bones of the ''os coxae'' (hip bone) tha ...

. It is thus a

biarticular muscle Biarticular muscles are muscles that cross two joints rather than just one, such as the hamstrings which cross both the hip and the knee. The function of these muscles is complex and often depends upon both their anatomy and the activity of othe ...

. 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 The tuberosity of the tibia or tibial tuberosity or tibial tubercle is an elevation on the proximal, anterior aspect of the tibia, just below where the anterior surfaces of the lateral and medial tibial condyles end. Structure The tuberosity ...

via the

patella The patella, also known as the kneecap, is a flat, rounded triangular bone which articulates with the femur (thigh bone) and covers and protects the anterior articular surface of the knee joint. The patella is found in many tetrapods, such as m ...

, where the

quadriceps tendon In human anatomy, the quadriceps tendon works with the Quadriceps muscle, quadriceps muscle to extend the leg. All four parts of the quadriceps muscle attach to the tuberosity of the tibia, shin via the patella (knee cap), where the quadriceps ten ...

becomes the

patellar ligament The patellar tendon is the distal portion of the common tendon of the quadriceps femoris, which is continued from the patella to the tibial tuberosity. It is also sometimes called the patellar ligament as it forms a bone to bone connection when ...

Other muscles

There is a small fifth muscle of the quadriceps complex — the

articularis genus muscle The articularis genus (also known as the subcrureus muscle) is a small skeletal muscle located anteriorly on the thigh just above the knee. Structure It arises from the anterior surface of the lower part of the body of the femur, deep to the v ...

— 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 The femoral nerve is a nerve in the thigh that supplies skin on the upper thigh and inner leg, and the muscles that extend the knee. Structure The femoral nerve is the major nerve supplying the anterior compartment of the thigh. It is the largest ...

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 Walking (also known as ambulation) is one of the main gaits of terrestrial locomotion among legged animals. Walking is typically slower than running and other gaits. Walking is defined by an 'inverted pendulum' gait in which the body vaults o ...

running Running is a method of terrestrial locomotion allowing humans and other animals to move rapidly on foot. Running is a type of gait characterized by an aerial phase in which all feet are above the ground (though there are exceptions). This is ...

jumping Jumping or leaping is a form of locomotion or movement in which an organism or non-living (e.g., robotic) mechanical system propels itself through the air along a ballistic trajectory. Jumping can be distinguished from running, galloping and ...

and

squatting Squatting is the action of occupying an abandoned or unoccupied area of land or a building, usually residential, that the squatter does not own, rent or otherwise have lawful permission to use. The United Nations estimated in 2003 that there ...

. 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 Manual therapy, or manipulative therapy, is a physical treatment primarily used by physical therapists, physiotherapists, occupational therapists to treat musculoskeletal pain and disability; it mostly includes kneading and manipulation of ...

and

physical therapy Physical therapy (PT), also known as physiotherapy, is one of the allied health professions. It is provided by physical therapists who promote, maintain, or restore health through physical examination, diagnosis, management, prognosis, patie ...

from repetitive strain injuries, such as from

skiing Skiing is the use of skis to glide on snow. Variations of purpose include basic transport, a recreational activity, or a competitive winter sport. Many types of competitive skiing events are recognized by the International Olympic Committee ...

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

Society and culture

Training

strength training Strength training or resistance training involves the performance of physical exercises that are designed to improve strength and endurance. It is often associated with the lifting of weights. It can also incorporate a variety of training te ...

, 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 In etymology, back-formation is the process or result of creating a new word via inflection, typically by removing or substituting actual or supposed affixes from a lexical item, in a way that expands the number of lexemes associated with the ...

, is frequently used.

Additional images

File:Knee diagram.svg, The quadriceps tendon connects to the top part of the kneecap (

) 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

References

External links

* * {{Authority control Knee extensors Thigh muscles Anterior compartment of thigh Muscles of the lower limb