Corpus: Anular ligament of the fingers

The annular bands are composed of dense connective tissue and are evenly distributed along the entire finger. Based on their respective locations, they are differentiated as follows:

• A1 annular band: approximately 5mm proximal to the metacarpophalangeal joint
• A2 annular band: the longest and strongest band, originating in the middle of the proximal phalanx
• A3 annular band: covering the proximal interphalangeal joint
• A4 annular band: at the level of the middle third of the middle phalanx
• A5 annular band: at the level of the distal interphalangeal joint, fused with the palmar plate and joint capsule

The ligaments annularia, together with the oblique ligaments, serve to guide the flexor tendons smoothly along the finger bones.

In the case of an injury to the a2-a4 annular bands, it can clinically lead to the bowstring phenomenon.