Which joint type allows movement in multiple planes, such as the shoulder?

Which joint type allows movement in multiple planes, such as the shoulder?

• A. Pivot joint
• B. Ball-and-socket joint
• C. Hinge joint
• D. Saddle

Answer: (B)

Movement in multiple planes comes from a ball-and-socket joint, where a spherical head fits into a cup-shaped socket. This design frees the joint to move in several directions and rotate around the long axis. In the shoulder, the glenohumeral joint is the classic example: the rounded humeral head sits in the shallow glenoid cavity of the scapula, and the surrounding capsule, ligaments, and muscles allow flexion/extension, abduction/adduction, internal and external rotation, and circumduction. Others are more limited: a pivot joint enables rotation around a single axis; a hinge joint bends and straightens in one plane; a saddle joint allows movement in two planes but not to the same extent or rotational freedom as a ball-and-socket.

Movement in multiple planes comes from a ball-and-socket joint, where a spherical head fits into a cup-shaped socket. This design frees the joint to move in several directions and rotate around the long axis. In the shoulder, the glenohumeral joint is the classic example: the rounded humeral head sits in the shallow glenoid cavity of the scapula, and the surrounding capsule, ligaments, and muscles allow flexion/extension, abduction/adduction, internal and external rotation, and circumduction.

Others are more limited: a pivot joint enables rotation around a single axis; a hinge joint bends and straightens in one plane; a saddle joint allows movement in two planes but not to the same extent or rotational freedom as a ball-and-socket.