If your thumb or finger gets stuck in a bent position, you probably have a condition called trigger finger. While it can be preceded by a hand injury or strain, trigger finger is most commonly associated with arthritis.
How trigger finger develops
Tendons control the movement of our fingers and thumbs. Each tendon is surrounded by a tendon sheath. A sheath is made of a delicate membrane, called a synovial membrane. If the membrane becomes inflamed and narrows, the tendon it encapsulates can have trouble moving. The tendon can catch on the sheath and get stuck, locking the finger in place.
Despite its name, trigger finger often affects the ring finger or thumb, and it can affect multiple digits at once. If you try to manually straightened your bent finger or thumb, it may snap straight out as the tendon moves again suddenly.
Arthritic conditions associated with trigger finger
Arthritis of any kind can cause inflammation in the joints, and that inflammation is not necessarily isolated and contained. The tissues of the hand and fingers are interconnected, and inflammation in one area of tissue can have cascading effects, including trigger finger.
Rheumatoid arthritis, psoriatic arthritis, and gout are three types of arthritis linked to trigger finger.
1. Rheumatoid arthritis (RA)
People who have rheumatoid arthritis have painful joint inflammation. The inflammation occurs when the immune system attacks the delicate lining that surrounds a joint.
Joint lining is a type of synovial membrane—the same kind of membrane that becomes inflamed in cases of trigger finger. It is not surprising that RA inflammation that affects the finger joints’ synovial membrane is associated with trigger finger.
2. Psoriatic arthritis
Like people who have RA, people who have psoriatic arthritis have painful joint inflammation. The inflammation caused by psoriatic arthritis primarily occurs where tendons and ligaments attach to bone tissue. These attachment points are called entheses.
If psoriatic arthritis causes a finger or thumb’s tendon enthesis to become inflamed, the connected tendon sheath may also become inflamed, causing trigger finger.
Research suggests that trigger finger may be a risk factor for psoriatic arthritis.1,2 If you have trigger finger and have other risk factors or signs of psoriatic arthritis, talk to your doctor about getting screened for the disease.
One of the most common forms of inflammatory arthritis is gout. This disease occurs when sharp, microscopic uric acid crystals build up in the soft tissue of a joint.
It’s possible for deposits of uric acid crystals to form nodules under the skin. These nodules are called tophi, and they most commonly develop when gout is chronic and untreated. Research suggests3,4 that tophi can irritate nearby tissue and lead to the inflammation of a finger or thumb’s tendon sheath, causing trigger finger.
Seeking care for trigger finger
If you have trigger finger, the best thing to do is consult with your primary care provider or an orthopedist who specializes in hands. If you think your trigger finger might be related to an undiagnosed arthritic condition (rather than a hand injury or overuse), talk to your doctor.