Trigger Finger

Painful Snapping of the Finger Tendons

trigger finger
A trigger finger causes a painful snapping sensation.. Marcela Barsse / Getty Images

Trigger finger is a common problem that causes pain and snapping of the tendons in the fingers. The problem that occurs in a patient who has trigger finger is due to the tendons of the fingers, and the sheath in which these tendons live.

The name trigger finger is the symptom of triggering or snapping of the finger. This occurs when relaxing a clenched finger or fist, the affected trigger finger remains flexed.

When enough force has been gathered, the trigger finger will suddenly snap into an extended position, like pulling a trigger.

Finger Tendons

The tendons in your fingers are like ropes that attach to the ends of your fingers. When your forearm muscles contract, the tendons pull the fingers into a fist. The tendons run part of their course through a sheath called the flexor tendon sheath. In patients who have a trigger finger, this mechanism of movement of the tendon within the sheath is not smooth.

Each finger tendon sheath is a thin tube that runs from the mid-palm towards the end of the finger.  The sheath is reinforced in several locations; this reinforced part of the sheath is called a pulley.  The first pulley on the tendon sheath (called the A1 pulley) is the location where a trigger finger is getting hung up.  In patients with a trigger finger, this is the location of pain when pressed in the palm of the hand.

Many patients have symptoms other than just a snapping sensation of the finger.  Other signs of a trigger finger can include a weakened grip and difficulty performing repetitive movements of the finger.  Many patients experience numbness of the fingers, although this is more commonly the result of carpal tunnel syndrome, which occurs frequently along with trigger finger.

Trigger Finger Causes

The cause of trigger finger is often unclear, and can seemingly appear from nowhere. It can occur in one or more fingers, and can occur at different times in different locations. Trigger finger results from a discrepancy between the size of the tendon and the size of the entrance to the tendon sheath. This discrepancy can be the result of localized inflammation or a nodular swelling on the tendon itself.

When the size discrepancy between the tendon and the tendon sheath reaches a critical point, the tendon will experience resistance from the tendon sheath. At first, this is felt as a snapping of the trigger finger when relaxing a fist. If the condition worsens, the trigger finger may need applied pressure from other fingers to straighten, or may not straighten at all.

Trigger finger is about 6 times more common in women than in men, and much more common in individuals with diabetes or rheumatoid arthritis. There has also been speculation that other factors such as genetic predisposition and occupational use can increase the chance of developing a trigger finger.

Trigger Finger Treatment

Trigger finger treatments may consist of simple steps, injections, or surgery. Often people start off with something simple, and if the symptoms persist or return, a more invasive treatment may be recommended. Some of the simplest treatments include splinting of the affected digit, physical therapy, and giving the problem some time to see if the symptoms resolve. 

Sources:

Adams JE, Habbu R. "Tendinopathies of the Hand and Wrist" J Am Acad Orthop Surg. 2015 Dec;23(12):741-50.

Saldana MJ. "Trigger Digits: Diagnosis and Treatment" J Am Acad Orthop Surg July/August 2001; 9:246-252.

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