Rotatory movements of forearm and hand about a vertical (longitudinal) axis at the superior and inferior radio-ulnar joints.

• Supination — palm faces anteriorly/upwards (anatomical position)
• Pronation — palm faces posteriorly/downwards

Axis of Rotation and Mechanism

• Axis passes through centre of head of radius (above) and ulnar attachment of articular disc of inferior radio-ulnar joint (below)
• Axis not stationary — lower end of ulna moves backwards and laterally in pronation, forwards and medially in supination
• Pronation: lower end of radius (with articular disc) rotates around relatively fixed ulna, crossing in front; head of radius rotates within fibro-osseous ring (annular ligament + radial notch of ulna)
• Supination: radius and ulna lie parallel

Range of Movement

• ~50° supination and ~50° pronation from midprone = sufficient for most activities

Muscles Producing the Movements

Supination vs Pronation — Why Supination is More Powerful

• Supination = antigravity movement
• Performed by more powerful muscles (biceps brachii)
• Pronation performed by weaker muscles (pronator quadratus + pronator teres)

Functional and Clinical Correlations

• “Kings pronate, beggars supinate” — king turns palm down; beggar turns palm up
• Tightening screw (right hand) = supination (more powerful); loosening = pronation
• Morphological significance: pronation for picking up food; supination to bring to mouth

Supination and pronation are rotatory movements of the forearm (and hand) about a vertical (longitudinal) axis, occurring at the superior and inferior radio-ulnar joints. In supination, the palm faces anteriorly/upwards (anatomical position); in pronation, the palm faces posteriorly/downwards.

Axis of Rotation and Mechanism

• The axis of rotation passes through the centre of the head of the radius above and through the ulnar attachment of the articular disc of the inferior radio-ulnar joint below.
• This axis is not perfectly stationary — the lower end of the ulna moves slightly backwards and laterally during pronation, and forwards and medially during supination, displacing the axis laterally in pronation and medially in supination.
• During pronation, the lower end of the radius (with the articular disc) rotates around the relatively fixed head of ulna, crossing in front of it; the head of the radius simultaneously rotates within the fibro-osseous ring formed by the annular ligament and the radial notch of the ulna.
• In supination, the radius and ulna lie parallel to each other.

Range of Movement

• Approximately 50° of supination and 50° of pronation from the midprone position are sufficient for most routine activities.

Muscles Producing the Movements

(For attachments and individual actions of these muscles, see Supinator, Biceps Brachii, and Pronators (Pronator Teres and Pronator Quadratus).)

Supination vs Pronation — Why Supination is More Powerful

• Supination is an antigravity movement in the anatomical position (turning the palm up works against gravity).
• Supination is performed by more powerful muscles (notably biceps brachii), whereas pronation is performed by relatively weaker muscles (pronator quadratus and pronator teres).

Functional and Clinical Correlations

• “Kings pronate, beggars supinate” — a mnemonic for the resting postures: a king turns the palm down (pronation) to dismiss/give, a beggar turns the palm up (supination) to receive.
• Screwing/unscrewing movements: Tightening a screw or nut/bolt with the right hand uses supination (the more powerful movement); loosening uses pronation.
• Morphological significance: Supination and pronation are thought to have evolved for feeding — food is picked up from a surface in pronation and brought to the mouth in supination.

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