Q. My finger hurts. When I try to bend and straighten it, it feels like it's catching. What's going on?
A. It sounds like you have trigger finger. This common condition is named for the trigger-like snap that occurs when the finger briefly locks and then suddenly releases as you try to bend or straighten it. Formally known as "stenosing tenosynovitis," it affects the pulleys and tendons in the hand.
When you think of all the things that our hands can do, it's amazing. Tying knots, opening jars, scratching an itch, playing Beethoven sonatas. (I don't care what you've seen on YouTube; only humans can play Beethoven sonatas.) How do our hands do all these things?
Think of your hand as a collection of bones, tendons and muscles. The tendons in your arms and hands are like the strings of a marionette. At one end of the tendon is a muscle, and at the other end is a bone. When the muscle pulls a tendon, the tendon pulls a bone.
Some tendons attach to your finger bones on the underside (the palm side) of the fingers and other tendons attach to the top side. Stretch your hand out flat, then make a fist. Do it again, and ask yourself if you felt anything moving in your arm. You should feel muscles on the underside of your arm tensing up. They engage the tendons that attach to the underside of your fingers, pulling the bones in your fingers into a ball.
Finger tendons glide through tunnels. The tunnels are formed by tough tissues that hold the tendons close against the bone.
If a tendon develops a knot or if the lining covering the tendon swells, the tendon has a harder time squeezing through the opening of the tunnel. This causes pain, popping or the catching feeling you described. When the tendon catches, the tunnel also becomes swollen and irritated, creating a vicious cycle. Sometimes the tendon becomes stuck in the tunnel and the finger can't be straightened or bent.
It's not clear what causes trigger finger. People who are older than 40 and who have arthritis, gout or diabetes are more prone to the problem, but we don't really know why.
Wearing a splint, taking anti-inflammatory drugs and getting a steroid injection in the area around the tendon can help break the cycle of inflammation and pain.
If your symptoms don't improve, surgery is an option. The operation opens the tunnel, allowing the tendon to glide through it more easily. This is a quick procedure that usually restores finger movement right away. Some people feel tenderness, swelling and discomfort for four to six weeks, or possibly longer. A full recovery often takes at least three months but can take up to a full year.
• Dr. Komaroff is a physician and professor at Harvard Medical School. Go to his website to send questions and get additional information: AskDoctorK.com