Ball and socket joints also allow flexion and extension. Flexion of the shoulder joint occurs when the humerus (upper arm) moves forwards from the rest of the body, which happens at the end of an ...

Hinge joints are protected by cartilage and synovial fluid, a gel that assists with lubricating motion in the body ... ball and socket, planar, pivot, saddle, and ellipsoid joints. A hinge joint ...

Four important synovial joints used in most sporting actions are the elbow and shoulder joints in the arm, and the knee and hip joints in the leg. The elbow and knee joints are both hinge joints.