Trigger finger limits finger movement. When you try to straighten your finger, it will lock or catch before popping out straight. Trigger finger is a condition that affects the tendons in your fingers or thumb.
The tendon sheath attaches to the finger bones and keeps the flexor tendon in place as it moves.
Tendons are tissues that connect muscles to bone. When muscles contract, tendons pull on bones. This is what causes some parts of the body to move.
The muscles that move the fingers and thumb are located in the forearm, above the wrist. Long tendons — called the flexor tendons — extend from the muscles through the wrist and attach to the small bones of the fingers and thumb.
These flexor tendons control the movements of the fingers and thumb. When you bend or straighten your finger, the flexor tendon slides through a snug tunnel, called the tendon sheath, that keeps the tendon in place next to the bones.
The flexor tendon can become irritated as it slides through the tendon sheath tunnel. As it becomes more and more irritated, the tendon may thicken and nodules may form, making its passage through the tunnel more difficult.
The tendon sheath may also thicken, causing the opening of the tunnel to become smaller.
If you have trigger finger, the tendon becomes momentarily stuck at the mouth of the tendon sheath tunnel when you try to straighten your finger. You might feel a pop as the tendon slips through the tight area and your finger will suddenly shoot straight out.
The thickened nodule on the flexor tendon strikes the sheath tunnel, making it difficult to straighten the finger.
The cause of trigger finger is usually unknown. There are, however, factors that put people at greater risk of developing it.
- Trigger fingers are more common in women than in men.
- They occur most frequently in people who are between the ages of 40 and 60 years.
- Trigger fingers are more common in people with certain medical problems, such as diabetes and rheumatoid arthritis.
- Trigger fingers may occur after activities that strain the hand.
Symptoms of trigger finger usually start without any injury, although they may follow a period of heavy hand use. Symptoms may include:
- A tender lump in your palm
- Catching or popping sensation in your finger or thumb joints