The range of motion at the PIPs and DIPs increases ulnarly. This angles the more ulnar fingers toward the thumb in flexion and there is greater closure of the grip on the ulnar side of the hand. These pulleys resist bowstringing of the flexor tendons. There are 5 annular pulleys and 3 cruciate pulleys located on each digit from 2-5 and 2 annular and 1 oblique pulley on the thumb. Inflammation can induce distension of the sheaths and ischemic injury to the tendons and nerves in the region.
Inflammation associated with the ulnar bursa can induce symptoms of carpal tunnel.
The ulnar bursa extends to cover the flexor tendons of the little finger. The flexor tendons in the other digits have independent synovial sheaths. There are individual synovial sheaths associted with the tendons of flexor pollicis and flexor carpi radialis. The four tendons of the extensor digitorum are enclosed in a single synovial sheath. Palmaris longus insertion.