What type of joint is the knee classified as?

The knee is classified as a hinge joint because it primarily allows movement in one plane, mainly flexion and extension. A hinge joint resembles a door hinge, where it allows one bone to move relative to another in a way that mimics the opening and closing of a door. In the case of the knee, this motion involves bending and straightening the leg.

While the knee does permit a small degree of rotational movement, it primarily functions according to the characteristics of a hinge joint, which is its main classification. Other types of joints, such as ball-and-socket joints, allow a much wider range of motion, including rotary movement, but this is not a principal function of the knee. Similarly, pivot joints enable rotational movement around a single axis, and fibrous joints are fixed, providing no movement. Thus, the classification of the knee as a hinge joint is accurate given the predominant type of movement it facilitates.