Supinator Tendon Insertion

tendo musculi supinatoris (insertio)

The supinator wraps around the lateral proximal radius in two layers with the posterior interosseous nerve passing between them. Its insertion on the anterior and lateral proximal radius makes it the primary forearm supinator at slow speeds and when the elbow is extended (when biceps supination is less efficient). PIN entrapment at the Arcade of Frohse within the supinator is the cause of PIN syndrome.

Region: Forearm

Biomechanics

Function & Actions

Forearm supination (the only supinator other than biceps); the posterior interosseous nerve runs through the supinator between its two layers

Clinical Relevance

Clinical Notes

Supinator syndrome (PIN entrapment) produces weakness of all wrist and finger extensors except ECRL and brachioradialis with no sensory loss. The Spinner test (resisted supination at 0 degrees of elbow flexion) stresses the supinator and reproduces PIN entrapment pain. Surgical decompression through the Frohse arcade restores PIN function.

Pathology

Common Injuries & Conditions

PIN Entrapment at the Arcade of Frohse

Posterior interosseous nerve compression within the supinator producing finger and wrist extensor weakness managed with surgical arcade decompression.