In trigger finger, stenosing tenosynovitis most commonly affects which pulley?

• A. A4 pulley
• B. A2 pulley
• C. A3 pulley
• D. A1 pulley

Answer: (D)

Stenosing tenosynovitis in trigger finger most commonly affects the A1 pulley, which sits at the level of the metacarpophalangeal joint. Repetitive use and friction in this area cause thickening of the pulley or a nodular change in the flexor tendon as it passes through the A1 pulley, leading to a narrowed canal that catches or locks during finger flexion. A palpable nodule may be felt at the MCP joint as the finger moves. The A1 pulley is the first annular pulley encountered along the tendon, so this location is the most susceptible to triggering. Pulleys further along the finger (A2, A3, A4) are less commonly involved in triggering and are more often linked to other tendon mechanics, such as bowstringing, rather than the classic triggering pattern at the MCP level.