Which joints are ball-and-socket joints?

• A. Elbow and knee
• B. Hip and knee
• C. Shoulder and elbow
• D. Shoulder and hip

Answer: (D)

Ball-and-socket joints allow movement in many directions because a rounded head fits into a cup-shaped socket, giving a wide range of motion in multiple planes. The joints that fit this description are the shoulder and the hip, which both permit flexion/extension, abduction/adduction, and rotation. The elbow and knee are hinge joints, mainly moving in one plane (bending and straightening), so they aren’t ball-and-socket. A combination involving the hip and knee mixes a ball-and-socket joint with a hinge joint, which isn’t a match. Therefore, the joints that are ball-and-socket are the shoulder and the hip.