Digital extensor mechanism

The common extensor tendon is maintained in a central position at the metacarpophalangeal joint level by radial and ulnar attachments to the Sagittal bands. The tendon trifurcates over the dorsum of the proximal phalanx. The central portion of the tendon, or Central slip, crosses the proximal interphalangeal joint and attaches to the dorsal base of the middle phalanx. The radial and ulnar slips pass palmar to join the intrinsic tendons from the interosseous and lumbrical muscles to form the Lateral bands. The lateral bands cross the lateral aspect of the proximal interphalangeal joint and are joined over the dorsum of the middle phalanx by the Triangular ligament to form the Terminal tendon. This crosses the dorsal surface of the distal interphalangeal joint to attach to the dorsal base of the distal phalanx.