pronationsupination

Pronationsupination, usually described as pronation-supination or forearm rotation, refers to the paired, opposing movements that rotate the forearm about its longitudinal axis. Pronation turns the palm to face downward or posteriorly when the elbow is extended, while supination turns the palm to face upward or anteriorly. These movements depend on rotation at the radioulnar joints, both proximal and distal, with the radius rotating around the ulna while the interosseous membrane helps transmit forces.

Anatomy and mechanics: The forearm consists of two long bones, the radius and ulna. Pronation occurs as the radius crosses over the ulna, increasing the angle between them at the distal radioulnar joint. Supination occurs when the two bones rotate in parallel, allowing the palm to face forward. The joints involved are the proximal and distal radioulnar joints, complemented by the elbow and wrist complexes during functional tasks.

Muscles: Pronation is primarily produced by the pronator teres and pronator quadratus. Supination is mainly driven by the supinator and the biceps brachii, with the latter contributing especially when the elbow is flexed. Other forearm muscles can assist depending on grip, speed, and load.

Range of motion and variation: In adults, typical ranges are about 70–90 degrees for pronation and 80–90 degrees for supination, though individual and age-related variation exists. Normal function supports many daily activities, such as turning a doorknob, using tools, or lifting objects.

Clinical relevance: Understanding pronation-supination is important in diagnosing forearm injuries and planning rehabilitation, as injuries to the radioulnar joints, interosseous membrane, or involved muscles can impair rotational dexterity and grip.