A joint is a junction of two or more bones. Joints impart motion and mobility in various activities such as walking, running, talking, sitting, arising etc.

        A joint capsule made of fibrous tissue encloses the free ends of the bones. It makes the joint compact and strong, and encloses the joint cavity filled with synovial fluid. The synovial fluid is secreted by the synovial membrane. The membrane is made up of cells and elastic tissue and has a rich blood supply. This fluid nourishes and lubricates the joint. The cartilage covers the free end of the bone, thereby protecting it from erosion during motion and loading. Cartilage is not as hard as the bone and does not show up in an X-Ray. It has viscoelastic properties. Muscles and tendons are attached close to a joint and are responsible for its motion. Along with ligaments, capsule and other supporting structure, they make the joint stable. Joint also has nerves which perceive pain. Some joints for example the spine and rib cage, do not have synovial membrane and only contain cartilage.