What are the knee and elbow joints classified as?

The knee and elbow joints are classified as hinge joints, which are designed to allow movement primarily in one plane, similar to the way a door opens and closes. This structural characteristic enables flexion and extension movements, which are the primary movements at these joints.

In the case of the elbow, it allows the forearm to move towards and away from the upper arm, whereas the knee facilitates bending and straightening of the leg. The hinge joint structure is primarily formed by the articulation of two or more bones where the bones' ends fit into each other, allowing for movement that primarily revolves around a single axis.

Other joint types, such as ball and socket joints, pivot joints, and gliding joints, serve different functional purposes and allow for different ranges of motion. For instance, ball and socket joints, like the shoulder or hip, allow for rotational movement and movement in multiple planes. Pivot joints enable rotation around a single axis, as seen in the neck. Gliding joints permit sliding movements, which are typically found in the small bones of the wrists and ankles. Understanding the specific functions and characteristics of these joint types helps clarify why the classification of the knee and elbow as hinge joints is accurate.