Knee

In humans and other primates, the knee joins the thigh with the leg and consists of two joints: one between the femur and tibia (tibiofemoral joint), and one between the femur and patella (patellofemoral joint). It is the largest joint in the human body. The knee is a modified hinge joint, which permits flexion and extension as well as slight internal and external rotation. The knee is vulnerable to injury and to the development of osteoarthritis.

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 many tetrapods, such as mice, cats, birds, and dogs, but not in whales, or most reptiles.

the back of your knee

thumb|upright=1.85|A boy kneeling in the courtyard of the Umayyad Mosque in Syria Kneeling is a basic human position where one or both knees touch the ground. According to Merriam-Webster, kneeling is defined as "to position the body so that one or both knees rest on the floor". Kneeling with only one knee, and not both, is called genuflection.

Wear and tear of the cartilaginous joint surfaces of the knee joint.

strike with the knee

Kneecapping is a form of malicious wounding, in which the victim is injured in the knee, often as torture. The injury is typically inflicted by a low-velocity gunshot to the back of the knee (popliteal fossa) with a handgun. The term is considered a misnomer by medical professionals, because only a very small minority of victims suffer damage to the kneecap. A review of eighty kneecapping victims found that only two had a fractured kneecap. Some victims have their elbows and ankles shot as well.

cartilage formation in the human knee

Fluid-filled sac of the knee joint