Trigger Finger Trigger finger is a condition that causes pain, stiffness, and a sensation of locking or catching when you bend and straighten your finger. The condition is also known as “stenosing tenosynovitis.” The ring finger and thumb are most often affected by trigger finger, but it can occur in the other fingers, as well. When the thumb is involved, the condition is called “trigger thumb.” Anatomy The flexor tendons are long cord-like structures that attach the muscles of the forearm to the bones of the fingers. When the muscles contract, the flexor tendons allow the fingers to bend. Each of the flexor tendons passes through a tunnel in the palm and fingers that allows it to glide smoothly as the finger bends and straightens. This tunnel is called the “tendon sheath.” Along the tendon sheath, bands of tissue called “pulleys” hold the flexor tendons closely to the finger bones. The tendons pass through the pulleys as the finger moves. The pulley at the base of the finger is called the “A1 pulley.” This is the pulley that is most often involved in trigger finger. Description In a patient with trigger finger, the A1 pulley becomes inflamed or thickened, making it harder for the flexor tendon to glide through it as the finger bends. Over time, the flexor tendon may also become inflamed and develop a small nodule on its surface. When the finger flexes and the nodule passes through the pulley, there is a sensation of catching or popping. This is often painful. In a severe case of trigger finger, the finger locks and becomes stuck in a bent position. Sometimes the patient must use his or her other hand to straighten the finger. Cause While the causes of trigger finger are not well known, several factors may increase your risk for developing the condition. These include: Medical conditions. Trigger finger is more common in people with certain medical conditions, such as diabetes and rheumatoid arthritis. Forceful hand activities. The condition is known to occur after forceful use of the fingers and thumb. Symptoms Symptoms of trigger finger often start without a single injury. They may follow a period of heavy or extensive hand use, particularly pinching and grasping activities. Symptoms may include: A tender lump at the base of the finger on the palm side of the hand A catching, popping, or locking sensation with finger movement Pain when you bend or straighten the finger Stiffness and locking tend to be worse after periods of inactivity, such as when you wake up in the morning. In a severe case, the involved finger may become locked in a bent position. Examination Your doctor will be able to diagnose a trigger finger by talking with you about your symptoms and examining your hand. Typically, x-rays or other tests are not needed. During the exam, your doctor will look for: Tenderness over the flexor tendon sheath in the palm of your hand Thickening or swelling of the tendon sheath Triggering when you bend and straighten your finger