The shoulder joint is best described as what type of joint?

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

Answer: (C)

Movement in multiple directions around a common center point is enabled by a ball-and-socket arrangement. The shoulder joint, or glenohumeral joint, has a spherical head of the humerus that fits into the shallow socket of the scapula (the glenoid fossa). This configuration allows flexion, extension, abduction, adduction, rotation, and circumduction, giving it one of the widest ranges of motion in the body. Stability comes from soft tissues—like the glenoid labrum, joint capsule, ligaments, and the rotator cuff tendons—rather than a deep bony fit, which is why the joint is so mobile but less inherently stable.

Hinge joints permit motion in one plane (like elbow flexion and extension), pivot joints rotate around a single axis (like the radius on the ulna), and saddle joints have concave and convex surfaces oriented to allow movement in two directions but still not the broad, three-dimensional mobility of a ball-and-socket joint.