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

muscle Muscle is a soft tissue, one of the four basic types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Muscle tissue gives skeletal muscles the ability to muscle contra ...

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

thigh In 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 bone tissu ...

. 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 (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg. The Femo ...

. 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

condyle A condyle (;Entry "condyle"
in

s): * 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 attach ...

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 The anterior inferior iliac spine (AIIS) is a bony eminence on the anterior border of the hip bone, or, more precisely, the wing of the ilium. Structure The AIIS is a bony eminence on the anterior border of the ilium. It is below the anterior ...

and from the superior edge of the

acetabulum The acetabulum (; : acetabula), also called the cotyloid cavity, is a wikt:concave, concave surface of the pelvis. The femur head, head of the femur meets with the pelvis at the acetabulum, forming the Hip#Articulation, hip joint. Structure The ...

. 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 The patella (: patellae or patellas), 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 m ...

, where the

quadriceps tendon In human anatomy Human anatomy (gr. ἀνατομία, "dissection", from ἀνά, "up", and τέμνειν, "cut") is primarily the scientific study of the morphology of the human body. Anatomy is subdivided into gross anatomy and micros ...

becomes the

patellar tendon 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 whe ...

Other muscles

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

cadaver A cadaver, often known as a corpse, is a Death, dead human body. Cadavers are used by medical students, physicians and other scientists to study anatomy, identify disease sites, determine causes of death, and provide tissue (biology), tissue to ...

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. It is the largest branch of the lumbar plexus. Structure The femoral nerve is the major nerve supplying the ant ...

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 In anatomy, extension is a movement of a joint that increases the angle between two bones or body surfaces at a joint. Extension usually results in straightening of the bones or body surfaces involved. For example, extension is produced by extend ...

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 as an " inverted pendulum" gait in which the body vaults o ...

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

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 wer ...

. 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 Gait is the pattern of Motion (physics), movement of the limb (anatomy), limbs of animals, including Gait (human), humans, during Animal locomotion, locomotion over a solid substrate. Most animals use a variety of gaits, selecting gait based on s ...

.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 treatment primarily used by physical therapists, occupational therapists, and massage therapists to treat musculoskeletal pain and disability. It mostly includes kneading and manipulation of muscle ...

and

physical therapy Physical therapy (PT), also known as physiotherapy, is a healthcare profession, as well as the care provided by physical therapists who promote, maintain, or restore health through patient education, physical intervention, disease preventio ...

from repetitive strain injuries, such as from

skiing Skiing is the use of skis to glide on snow for basic transport, a recreational activity, or a competitive winter sport. Many types of competitive skiing events are recognized by the International Olympic Committee (IOC), and the International S ...

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

Society and culture

Training

strength training Strength training, also known as weight training or resistance training, is exercise designed to improve physical strength. It is often associated with the lifting of Weightlifting, weights. It can also incorporate techniques such as bodyweigh ...

, the quadriceps are trained by several leg exercises including the squat, leg press, and

leg extension The leg extension is a resistance weight training exercise that targets the quadriceps muscle (m. quadriceps femoris) in the legs. The exercise is done using a machine called the Leg Extension Machine. There are various manufacturers of these mach ...

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 Back-formation is the process or result of creating a neologism, new word via Morphology (linguistics), morphology, typically by removing or substituting actual or supposed affixes from a lexical item, in a way that expands the number of lexemes ...

, 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