supinaatio

Supinaatio, commonly called supination, is a movement that rotates a limb to turn the palm to face anteriorly in the forearm or the sole of the foot to face medially. In biomechanics, the term is used for both forearm rotation and a medial-oriented turning of the foot, depending on context.

In the forearm, supination occurs when the radius rotates around the ulna so that the two bones run parallel. This action is produced mainly by the biceps brachii and the supinator muscle, and it involves the proximal and distal radioulnar joints. Supination is opposite to pronation, which is produced by the pronator teres and pronator quadratus.

In the foot, supination describes a position in which the foot inverts (the sole turns inward), adducts, and plantarflexes. This combined movement tightens the medial arch and typically occurs during the toe-off phase of gait. Muscles contributing to foot supination include the tibialis posterior and tibialis anterior, among others. Abnormalities in foot supination—whether excessive, limited, or improperly coordinated—can affect gait and predispose to certain injuries.

Clinical relevance: the ability to assess and manage forearm pronation–supination and foot supination is important in sports medicine, orthopedics, and physical therapy. Conditions may include forearm injuries that impair rotational motion, or structural and functional foot issues that alter gait patterns.

Etymology: the term derives from Latin supinatio, from supinus meaning lying on the back.