Which joint classification applies to the knee joint?

The knee joint is classified as a hinge joint because it primarily allows for movement in one plane, specifically flexion and extension. This characteristic is similar to the way a door hinge operates, permitting the bones of the leg to bend and straighten as the knee joint moves. The structure of the knee includes the femur (thigh bone) and the tibia (shin bone), which are connected by ligaments and muscles that reinforce stability while allowing for this specific range of motion.

In contrast, fibrous joints typically allow little to no movement and are connected by dense connective tissue, making them unsuitable for the knee's articulation requirements. Saddle joints, found in the thumbs, enable a wider range of motion, including back-and-forth and side-to-side movements, which the knee does not perform. Cartilaginous joints, such as those found in the spine, allow for limited movement through cartilage and do not fit the knee joint's functional characteristics, which emphasizes its role as a hinge joint. Thus, the unique function and anatomical structure of the knee joint firmly categorize it as a hinge joint.