Trigger finger

What is trigger finger?

A trigger finger (also known as stenosing flexor tenosynovitis) is a finger that becomes 'locked' after it has been bent (flexed) or locked in a bent position. It is difficult to straighten out without pulling on it by the other hand.

You may hear a popping or clicking sound when it is pulled straight. This clicking may be worse in the morning. Sometimes there is mild pain and/or a small swelling at the base of the affected finger or thumb.

One or more fingers may be affected. Trigger finger most commonly affects your little finger, ring finger or thumb. It is actually more common in the right hand.

Diagram: trigger finger

What causes trigger finger?

The cause is often not clear. It is thought to be due to some inflammation which causes swelling of a tendon or the covering of the tendon (tendon sheath).

• A tendon is a strong tissue that attaches a muscle to a bone. In this case the tendon comes from a muscle in the forearm. It passes through the palm and attaches to the finger bone. The muscle pulling on this tendon bends (flexes) the finger towards the palm.

• A tendon sheath is like a tunnel that covers and protects parts of a tendon. Normally, the tendon slides easily in and out of the sheath as you bend and straighten the finger. In trigger finger the tendon can slide out of the sheath when you bend your finger. However, it cannot easily slide back in due to the swelling. The finger then remains bent (flexed) unless you pull it straight with your other hand.

Most cases occur for no apparent reason in healthy people. Around 2 in 100 people develop trigger finger. It is more common if you are aged over 40 and if you are female. It may also be more likely to develop if you have had a previous injury to your palm or finger.

In some cases it occurs after you have used your palm a lot - for example, it can happen:

• After jobs which involve a lot of screwdriver use.

• After working with tools that press on the palm.

These may cause some inflammation in the palm.

Sometimes trigger finger occurs as a feature of another disease. For example, trigger finger is more common in people with rheumatoid arthritis, amyloidosis, diabetes, underactive thyroid gland, Dupuytren's contracture and carpal tunnel syndrome and in people on dialysis. In these situations you will have other symptoms of the condition and the trigger finger is just one feature.

Note: most people with trigger finger do not have any of these conditions.

What is the treatment for trigger finger?

Not treating is an option at first

Around one in five people will improve without any treatment. Simply resting the hand and fingers, allowing any inflammation to settle, may resolve the problem without the need for treatment. You may be advised to take a painkiller (for example, paracetamol or ibuprofen) to relieve the pain.

Splinting

Your symptoms may improve if your finger (or trigger thumb) is strapped to a plastic splint so that it is completely straight. Some people wear a splint just at night.

A steroid injection

A steroid injection into the tendon sheath is one treatment if the condition does not settle. The steroid is combined with a local anaesthetic to make the injection less painful.

Steroids work by reducing inflammation. A finger splint may be advised for a few days after the injection to rest the finger. This treatment works in about 9 in 10 cases. A second injection may be needed if the first does not work.

Surgery

An operation done under local anaesthetic may be advised if the above does not work. A small cut is usually made at the base of the finger and the tendon sheath is widened. The surgical treatment of trigger finger is usually very successful.

An alternative operation is a percutaneous trigger finger release. A needle is used to release the tight mouth of the tunnel so an open operation is avoided.

If you have rheumatoid arthritis, these types of surgery may not be suitable for you. If you do need surgery, you may be offered an operation to remove part of the tendon sheath instead.

However, with an operation there is a small risk of damaging the tiny finger nerve and causing some numbness to the finger. Also, as with any operation, there is a small risk of any wound becoming infected.