Supinator Tendon

tendo musculi supinatoris

The supinator muscle has two heads (superficial from the lateral epicondyle and radial collateral ligament, and deep from the supinator crest of the ulna) that wrap around the proximal radius to insert on the lateral proximal radial shaft. The deep head of the supinator forms the arcade of Frohse (a fibrous arch at the proximal supinator origin) through which the posterior interosseous nerve (PIN) passes. Supinator acts to supinate the forearm with the elbow in any position.

Region: Forearm

Clinical Relevance

Clinical Notes

The supinator and specifically the arcade of Frohse is the primary site of PIN compression in posterior interosseous nerve syndrome, producing weakness of wrist and finger extension without sensory loss (the PIN is pure motor at this level). The arcade of Frohse is a fibrous arch at the proximal superficial supinator edge, variably present as a fibrous cord (compressive) or a free edge (non-compressive). Surgical decompression by releasing the arcade relieves the compression. The supinator tendon origin at the lateral epicondyle contributes to lateral epicondylitis when inflamed alongside the ECRB.

Pathology

Common Injuries & Conditions

Posterior Interosseous Nerve Compression at Arcade of Frohse

The fibrous arcade of Frohse at the proximal superficial supinator head compresses the PIN, producing painless progressive weakness of finger and wrist extension without sensory loss; EMG confirms the lesion at the supinator level and surgical release of the arcade through a Thompson posterior interosseous approach provides full motor recovery in acute cases.