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the area around the knee joint, a hinge joint that is one of the largest joints of the body, sustaining great pressure. The knee is formed by the proximal portion of the tibia, the distal end of the femur, and the patella, or kneecap. The bones are joined by ligaments, and the patella is secured to the adjacent bones by powerful tendons. The fibula is attached at the side of the knee to the tibia. Two crescent-shaped pads of cartilage, one medial and one lateral, called menisci, lying on top of the tibia cushion it from the femur and form the gliding surfaces of the joint in motion. Further cushioning is supplied by bursae, which are located around the main joint, between it and the patella and on the outside of the patella. A capsule of ligaments binds the whole assembly together. The capsule is lined with synovial membrane, which secretes a lubricating synovial fluid that makes possible a smooth, gliding motion. Traumatic disorders of the knee are common and include dislocation, sprain, and fracture.
Left: Knee joint, front view. Right: Knee joint, flexed in profile.
knee jerk (knee reflex) a kick reflex produced by sharply tapping the patellar ligament. To test this reflex, the lower part of the leg is allowed to hang relaxed (such as by crossing the legs at the knees) and the examiner taps the ligament below the patella with a small rubber hammer. The normal reaction is contraction of the quadriceps muscle, causing involuntary extension of the lower leg. This is a stretch reflex; striking the patellar ligament stretches the quadriceps muscle at the front of the thigh and causes it to contract. Two nerves are involved; one receives the stimulus and transmits the impulse to the spinal cord, and the other, a motor nerve, receives the impulse and relays it to the quadriceps muscle. Inadequate response to the knee jerk test may mean that the reflex mechanism involved is in some way impaired. In some people with normal reflexes the jerk of the knee is so light as to be nearly imperceptible, and the examiner must make other tests to check the reflex mechanism. Called also patellar or quadriceps reflex.


(), [TA]
1. Synonym(s): genu (1)
2. Any structure of angular shape resembling a flexed knee.
[A.S. cneōw]


1. genu; the area around the articulation of the femur and tibia.
2. any structure resembling this part of the leg.

housemaid's knee  inflammation of the bursa of the patella, with fluid accumulating within it.
knock knee  knock-knee.
trick knee  a popular term for a knee joint susceptible to locking in position, most often due to longitudinal splitting of the medial meniscus.


a. The joint between the thigh and the lower leg, formed by the articulation of the femur and the tibia and covered anteriorly by the patella.
b. The region of the leg that encloses and supports this joint.
2. An analogous joint or part of a leg of a quadruped vertebrate.
3. The joint between the femur and the tibia in an insect leg.


Etymology: AS, cneow
a joint complex that connects the thigh with the leg. It consists of three condyloid joints, 12 ligaments, 13 bursae, and the patella. The motion of this joint is not a simple gliding motion because the articular surfaces of the bones involved are not mutually adapted to each other. Various orthopedic conditions such as arthritis commonly affect the knee, especially in elderly individuals. The knee is relatively unprotected by surrounding muscles and is often injured by blows, sudden stops, and turns, especially those associated with sports. Ligament tears of the knee joint are extremely common in athletes and produce a variety of signs and symptoms, such as effusion, varying degrees of edema, differences in the shape of the knee joint, tenderness on palpation, crepitation, instability of the knee joint, and possible ecchymosis. Torn menisci are very common sports injuries and can cause severe pain, limping, edema, and greatly reduced motion.


() [TA]
1. Synonym(s): genu (1) .
2. Any structure of angular shape resembling a flexed knee.
[A.S. cneōw]


Enlarge picture
Enlarge picture
1. The articulations formed by the distal femur, proximal tibia, and the patella. See: illustration
2. Any structure shaped like a semiflexed knee. Synonym: geniculum

Brodie knee

See: Brodie, Sir Benjamin Collins

carpetlayer's knee

Prepatellar bursitis.

game knee

A colloquial term for internal derangement of the knee joint, characterized by pain or instability, locking, and weakness. It is usually the result of a torn internal cartilage, a fracture of the tibial spine, or an injury to the collateral or cruciate ligaments.

First Aid

The knee should be immobilized with a posterior splint.


Arthroscopy and/or magnetic resonance imaging may be necessary for a definitive diagnosis.

housemaid's knee

Prepatellar bursitis.

knee of internal capsule

The curve at the meeting place of the anterior and posterior limbs of the internal capsule of the brain.

jumper's knee

A colloquial term for an overuse syndrome, marked by chronic inflammation and infrapatellar tendonitis, resulting from repetitive jumping or leg extension exercises. The usual treatment is nonsteroidal anti-inflammatory drugs, rest, and phonophoresis.

locked knee

A condition in which the leg cannot be extended. It is usually due to displacement of meniscal cartilage or dislocation of the patella.

posterolateral corner knee

The ligamentous, capsular, and muscular structures that stabilize the knee against varus, external rotation, and anterior/posterior forces. Disruption of these structures can result in posterolateral rotary instability of the knee.

replacement of knee

Orthopedic implantation of a prosthetic knee joint, particularly useful in treating patients with severe disabling arthritis of the knee. See: arthroplasty

roofer's knee

Prepatellar bursitis.

runner's knee

A colloquial term for several overuse conditions resulting from excessive exercise of the lower extremities. These may involve the extensor mechanism and other musculotendinous insertions. Patellar tendonitis (jumper's knee), patellofemoral dysfunction, iliotibial band syndrome, and pes anserinus tendonitis or bursitis have all been called by this term.

valgus knee

A medial alignment of the femur and tibia of less than 180°.
Synonym: bandy leg; bowleg; genu valgum; tibia valga See: valgus

varus knee

A lateral alignment of the femur and tibia of greater than 195°.
Synonym: genu varum See: varus


The hinge articulation between the lower end of the thigh bone (FEMUR) and the upper end of the main lower leg shin bone (TIBIA). The knee cap (PATELLA) is a flat bone lying within the massive tendon of the thigh muscles and is not an intrinsic part of the joint.


  1. the joint between the femur and tibia of the posterior limb in higher vertebrates.
  2. a stem joint in grasses.
  3. a root emerging above ground or water level in trees inhabiting wet areas.


ginglyomoarthroidal joint between inferior femur and superior tibia; permits sagittal-plane flexion and extension of tibia on femur, and transverse rotation of femur on (static) weight-bearing tibia; at any one time only a small area of each convex femoral condyle articulates with the central area of each slightly concave tibial condyle; the space at the periphery of these articulations is infilled by a C-shaped rim of fibrocartilage (menisci) which deepen the articular cup for the distal femur; assists leg shock absorption and deceleration mechanisms (maximum foot pronation coincides with knee flexion during the gait cycle)
  • clergyman's knee; infrapatellar bursitis infrapatellar bursal inflammation and swelling due to chronic trauma, e.g. prolonged kneeling

  • housemaid's knee; prepatellar bursitis prepatellar bursal inflammation and swelling due to chronic trauma, e.g. prolonged scrubbing a floor

  • kneecap see patella

  • knock knee genu valgum; normal childhood positional variant of the knee joint (e.g. children from 2 to 6 years); thence resolves spontaneously, but may persist into adulthood, creating functional hindfoot varus (see genu valgum)

  • locked knee prevention of knee movement due to pain, swelling or arthropathy

  • overuse knee injury variable and varying, generalized or localized knee pain secondary to altered knee alignment or altered synchronicity of lower-limb function (+ associated lower-limb pathomechanical problem [e.g. excess foot pronation; tibial varum]) or muscular imbalance increasing knee misalignment; treatment includes diagnosis of pathomechanical problem by gait analysis, bespoke corrective orthoses, and rehabilitative exercises (Table 1 and Table 2)

  • rotational knee pain knee pain caused by excessive horizontal plane rotation (torque), e.g. excessive subtalar joint pronation leading to knee joint capsular strain and associated mistracking of patella and medial collateral ligament

Table 1: Stages in the pathology of chondromalacia patellae
StageClinical features
ISoftening or degeneration of the articular cartilage
IICleaving of articular cartilage
IIICleaving and fronding of the articular cartilage
IVErosion of cartilage and underlying bone sclerosis
Table 2: Biomechanical problems associated with predisposition to overuse knee injury
Knee stiffnessThe knee is fully extended at heel strike and should flex easily immediately after heel strike to facilitate the absorption of the shock of heel strike
Knee flexion is facilitated by transverse plane motion where the medial condyle of the distal femur rotates medially on the medial platform of the superior tibia; where transverse plane motion is limited (as in coxa valga/genu varum, coxa vara/genu valgum) knee flexion will be less efficient
Where knee flexion is compromised, increased stress is imposed on its structures
Loss of subtalar joint (STJ) pronationShock absorption is also facilitated by STJ pronation; where STJ pronation is limited (as in hindfoot varus or tibial varum) or where the STJ functions routinely at the limit of its range of motion (such as in an abducted foot ± hallux limitus), greater forces are transmitted to the knee with resultant tissue strain
Structure of the kneeThe collateral ligaments of the knee and the menisci are at greatest risk of injury at the point of maximum foot pronation and knee flexion
Ground reaction force (GRF)STJ pronation and knee flexion are initiated by GRF; GRF increases tibial shearing forces which, combined with femoral rotation, can induce knee injury
Excess foot pronationKnee extension creates a stable support limb during propulsion
During propulsion the pelvis and femur rotate externally, but the weight-bearing tibia cannot rotate externally if the foot is excessively pronated, creating a torque on the knee joint, medial knee strain and patellofemoral pain
Gastrocnemius actionDuring knee extension the gastrocnemius is passively stretched and maximally efficient, allowing transfer of power from the quadriceps to the ankle. Once the knee is flexed, gastrocnemius is relaxed and not efficient, and only soleus contraction effects ankle plantarflexion

Knee injuries may be induced by transverse-plane compensation for structural deformities in the lower leg or foot.


() [TA]
1. Synonym(s): genu (1) .
2. Any structure of angular shape resembling a flexed knee.
[A.S. cneōw]


n a joint complex that connects the thigh with the lower leg. It consists of 3 condyloid joints, 12 ligaments, 13 bursae, and the patella.


in large animals, the carpus; in small animals, the stifle. See Table 11.

bench knee
conformation defect in which the metacarpus is not centered symmetrically to the carpus.
blemished knee
scarred or otherwise imperfect appearance.
broken knee
used to mean that a horse has fallen and broken the skin over the carpus.
knee gall
see knee thoroughpin (below).
knee jerk
see patellar reflex.
popped knee
knee spavin
an old-fashioned name for chronic carpitis in horses.
knee strap
a short strap used to strap up a horse's leg in a flexed position so that it is as immobile as a three-legged horse. A good form of restraint for a horse that is rearing.
knee thoroughpin
distention of the carpal sheath in the horse. Visible as a fluid-filled distention at the back of the knee.

Patient discussion about knee

Q. Can knee pain at childhood be connected to osteoarthritis? My mother is suffering from osteoarthritis (OA). She is 72 years old and the OA is a major problem in her life. My son is 10 years old. He has a relapsing knee pain. His pain occurs mostly at day time but can wake him from sleep. The pain is in both legs. Is my son in a risk group for OA?

A. Osteoarthritis is a disease that is most commonly caused by weight gain. The problem is that weigh gain has an important genetic factor. So, it doesn't matter if your son has knee pain right now, he is in a risk group for OA. If your mom is fat, she can start a program to lower her fat rate. I used this program for me. In the beginning it was too hard so cut her some slack!

Q. how to treat knee pain nothing

A. to treat it properly you need to define it and understand the cause. to help you do that there is a wonderful site that does a short servy and help you define where your knee pain comes from:

hope it helps!

Q. I have a reccurent ache just below my knee. what can it be? I am a 18 years old healthy guy. I never go to my physician, because i never need him, but in the past 4 month i recognized a strange pain just under my knee. The area is tender to palpation and the pain excruciate during walking and running. What can it be? What can I do to prevent it? P.S. I play collage basketball and this pain ruins my games...

A. Hi mate.
I am a 21 collage student and i play soccer.
It sure sounds like something i suffered from. Go see your GP and don't worry. if it is what i had he will probably tell you that
you can take any NSAID you want, and if you will give yourself a break from competitive sport for a month or so you will be just like new :)

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