Trigger finger - Causes of trigger finger

Trigger finger is usually caused by swelling of one of the tendons that run along your fingers and thumbs, although the exact reason why this occurs is not fully understood.

This swelling makes it difficult for your tendon to slide through the tunnel surrounding the affected tendon (the tendon sheath), causing the pain and stiffness associated with trigger finger.

The swelling can then lead to a section of tendon becoming bunched into a small lump (nodule) at the base of the affected finger or thumb – a bit like pulling a piece of string through a hole that is too small.

If a nodule forms, the tendon can get stuck in the tendon sheath, causing the affected finger or thumb to become temporarily stuck in a bent position. The affected tendon may then suddenly pop through the sheath, releasing your finger like the release of a trigger.

Who is most at risk?

The exact cause of trigger finger is not fully understood and, in most cases, is never known. However, several things may increase your risk of developing trigger finger:

your gender – trigger finger is more common in women than men
your age – trigger finger is more common in adults in their 40s and 50s
a previous hand injury – trigger finger may be more likely to develop after injuring the base of your finger or palm

Other health conditions

You may be more likely to develop trigger finger if you have any of the following conditions:

diabetes – a long-term condition that causes a person's blood sugar level to become too high
rheumatoid arthritis – a long-term condition caused by a problem with your immune system (the body’s defence system), resulting in pain and stiffness in your joints
gout – a short-term condition that causes inflammation (swelling) in one or more of your joints
amyloidosis – a condition where an abnormal protein called amyloid builds up in organs, such as your liver
underactive thyroid – where your body does not produce enough of certain hormones
carpal tunnel syndrome – a condition that affects the nerves in your wrist, causing pain and tingling
Dupuytren’s contracture – a condition that causes one or more fingers to bend into the palm of your hand
De Quervain’s disease – a condition that affects the tendons in your thumb, causing pain in your wrist