It is a ring surrounding radial head, attached to anterior and posterior margins of radial notch of ulna
Complex formed from capsule, lateral collateral ligament complex (LCLC) and supinator muscle
Tight superiorly, loose inferiorly
Best shown on axial and sagittal MRA
Anterior attachment: single band, broader
Posterior attachemnt: single to 4 bands (hence should not be mistaken for pathology)
On sagittal: funnel shaped, wider proximally, and narrow distally at radial neck
Nursemaid's elbow:
Transverse tear of the distal attachment of annular ligament is likely to be the first step.
Reference:
1. Sanal HT et al. Annular Ligament of the Elbow: MR Arthrography Appearance With Anatomic and Histologic Correlation. AJR 2009; 193:W122-W126
