A1 pulley is part of which anatomical structure?

• A. Flexor tendon sheath
• B. Extensor tendon sheath
• C. Ulnar collateral ligament
• D. Radial collateral ligament

Answer: (A)

The main idea is how the finger’s flexor tendons are organized to work efficiently. The A1 pulley is part of the flexor tendon sheath—the fibrous tunnel that wraps the flexor tendons as they bend at the fingers. It is the first annular pulley, located near the metacarpophalangeal joint, and it works with the other pulleys to keep the tendons pressed close to the bone during flexion. This close setup prevents bowstringing and helps the tendons transmit force effectively when you curl your fingers.

It is not a ligament; ligaments such as the collateral ligaments stabilize joints rather than enclosing tendons. It also isn’t the extensor tendon sheath, which surrounds the extensor tendons on the back of the hand. Clinically, thickening or inflammation of this pulley can lead to trigger finger due to restricted tendon glide.