Which joint allows for the greatest range of motion in the upper extremity?

The glenohumeral joint, commonly known as the shoulder joint, allows for the greatest range of motion in the upper extremity. This joint is a ball-and-socket type of joint, which facilitates movement in multiple planes and directions. It enables a wide variety of movements, including flexion, extension, abduction, adduction, internal rotation, and external rotation. The structure of the shoulder joint promotes this extensive range of motion, supported by a shallow glenoid fossa and a highly mobile humeral head.

In comparison, the elbow joint primarily allows for flexion and extension, which significantly limits its functional range of motion. The proximal radioulnar joint, while critical for rotational movement (pronation and supination), does not offer the same diversity of motion as the glenohumeral joint. The acromioclavicular joint plays a role in shoulder girdle movement and stability but is also limited in its range compared to the expansive motion capabilities provided by the glenohumeral joint. Therefore, the glenohumeral joint stands out as the primary joint responsible for the upper extremity's broad range of movement.