The five annular (A1-A5) and three cruciate pulleys of each finger form the fibro-osseous flexor tendon sheath. The A2 pulley (at the proximal phalanx) and A4 pulley (at the middle phalanx) are biomechanically critical. Their loss produces tendon bowstringing and significant flexion force reduction. Rock climbers stress the A2 pulley maximally during crimping, making it the most common pulley injury in climbing.
| Origin | Palmar surface of the proximal phalanx (A2) and middle phalanx (A4), from the bony margins on one side of the shaft |
|---|---|
| Insertion | Arches over the flexor tendons to the opposite margin of the same phalanx |
Hold the flexor tendons close to the bone so finger flexion is efficient and the tendons do not bowstring
A2 pulley rupture in rock climbers produces a palpable and audible pop during crimping, followed by bowstringing visible when the finger is flexed. MRI or ultrasound confirms the injury. Most partial tears heal conservatively with ring splinting; complete A2 tears may require pulley reconstruction with a tendon graft. The A2 pulley must be preserved during Zone II flexor tendon surgery.
A2 pulley rupture during rock climbing producing bowstringing and audible pop managed with ring splinting for partial tears and pulley reconstruction for complete tears.
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