What type of joint is found in the knees and elbows?

The knee and elbow joints are classified as hinge joints because they primarily allow movement in one plane, similar to the motion of a door hinge. In hinge joints, the surfaces of the bones are shaped in such a way that they enable flexion and extension—motion that bends and straightens the limb.

In the case of the elbow, the structure allows the forearm to move toward and away from the upper arm, while the knee joint permits the lower leg to flex and extend relative to the thigh. This distinct one-dimensional movement is characteristic of hinge joints, contrasting with the more complex multi-dimensional movements seen in ball-and-socket joints or the unique movements provided by saddle and ellipsoid joints. Therefore, the classification of both the knee and elbow as hinge joints reflects their functional anatomy and the specific range of motion they facilitate.