In trigger finger, also known as stenosing tenosynovitis, one of your fingers or your thumb gets stuck in a bent position and then straightens with a snap – like a trigger being pulled and released. If severe enough, the finger may become locked in a bent position. Trigger finger limits finger movement. When you try to straighten your finger, it will lock or catch before popping out straight.

Trigger finger can be painful and cause stiffness and tenderness, but often it’s more annoying than limiting.

The cause of trigger finger is a narrowing of the sheath that surrounds the tendon in the affected finger (flexor tendon). Tendons are fibrous cords that attach muscle to bone. Each flexor tendon is surrounded by a protective sheath. If the protective sheath becomes inflamed, frequently or for long periods, the space within the tendon sheath can become narrow and constricting. The tendon can’t glide through the sheath easily, at times catching the finger in a bent position before popping straight. With each catch, the tendon itself becomes more irritated and inflamed, worsening the problem. With prolonged inflammation, scarring and thickening (fibrosis) can occur and nodules can form, making the passage of the tendon through the tunnel more difficult.