Merriam-Webster's Collegiate® Dictionary, 11th Edition
KNEE
I. noun
Usage: often attributive
Etymology: Middle English, from Old English cnēow; akin to Old High German kneo knee, Latin genu, Greek gony Date: before 12th century
1. a joint in the middle part of the human leg that is the articulation between the femur, tibia, and patella, b. the joint in the hind leg of a four-footed vertebrate that corresponds to the human knee, the carpal joint of the foreleg of a four-footed vertebrate, the tarsal joint of a bird, the joint between the femur and tibia of an insect, something resembling the human knee: as, a piece of timber naturally or artificially bent for use in supporting structures coming together at an angle (as the deck beams of a ship), a rounded or conical process rising from the roots of various swamp-growing trees , the part of a garment covering the knee, a blow with the bent knee, kneed adjective
II. transitive verb (kneed; kneeing) Date: before 12th century to bend the knee to, to strike with the knee