Upper limb

Annular ligament of the radius

Ligamentum anulare radii

Origin

Anterior margin of the radial notch of the ulna

Insertion

Posterior margin of the radial notch of the ulna, encircling the radial head

Function

Encircles and secures the radial head against the ulna during forearm pronation and supination

Innervation

Deep radial nerve / posterior interosseous nerve (C5–C7)

Movement & chain

Permits 150°–180° pivot rotation of the radial head during pronosupination

Palpation

Palpable just distal to lateral epicondyle during forearm rotation

Clinical

Nursemaid's elbow / pulled elbow (radial head subluxation beneath annular ligament in young children); Monteggia fracture-dislocation.

Segmental innervation

C5–C7

In clinical practice

Closed reduction maneuver (supination-flexion or hyperpronation) for nursemaid's elbow

Region in the model

Upper limb