Noun

Singular knee

Plural knees

knee (plural knees)

1. In humans, the joint in the middle part of the leg.

   Jessica was wearing shorts, so she skinned her exposed knees when she fell.

2. (anatomy) The joint, or region of the joint, between the thigh and leg.
3. (anatomy) In the horse and allied animals, the carpal joint, corresponding to the wrist in humans.
4. (shipbuilding) A piece of timber or metal formed with an angle somewhat in the shape of the human knee when bent.
   • 1980, Richard W. Unger, The Ship in the Medieval Economy 600-1600, page 41

     Deck beams were supported by hanging knees, triangular pieces of wood typically found underneath the timbers they are designed to support, but in this case found above them.

5. (archaic)An act of kneeling, especially to show respect or courtesy.

   Give them title, knee, and approbation. Shak.

   To make a knee.

6. Any knee-shaped item or sharp angle in a line, "the knee of a graph", an inflection point
7. A blow made with the knee; a kneeing

Derived terms

• down on one's knees
• kneecap
• kneejerk
• kneel
• kneepan
• knees-up

The knee joint joins the thigh with the leg and consists of two articulations: one between the femur and tibia, and one between the femur and patella. It is the largest and most complicated joint in the human body. The knee is a mobile trocho-ginglymus (i.e. a pivotal hinge joint), which permits flexion and extension as well as a slight medial and lateral rotation. Since in humans the knee supports nearly the whole weight of the body, it is the joint most vulnerable both to acute injury and the development of osteoarthritis.

Human anatomy

The knee is a complex, compound, condyloid variety of a synovial joint. It actually comprises three functional compartments: the femoropatellar articulation consists of the patella, or "kneecap", and the patellar groove on the front of the femur through which it slides; and the medial and lateral femorotibial articulations linking the femur, or thigh bone, with the tibia, the main bone of the lower leg. The joint is bathed in synovial fluid which is contained inside the synovial membrane called the joint capsule.

Upon birth, a baby will not have a conventional knee cap, but a growth formed of cartilage. In human females this turns to a normal bone knee cap by the age of 3, in males the age of 5.