Does your finger get stuck when you bend it? And you have to prize it open with your other hand?
Congratulations, you have Trigger Finger. So named because it is caused by inflammation of the flexor tendons of the fingers or thumb, such as often happens with resisted, repetitive tasks like pulling the trigger of a pistol during firearms practice. This is a nuisance problem but can be quite disconcerting, as it feels like you’re losing control of the finger. Initially it seems a novelty, but can become quite painful and frustrating if not managed appropriately.
Tendons are surrounded by a sheath, which secretes a lubricating fluid to allow the tendon to slide freely back and forth with minimal friction. If a tendon becomes inflamed due to excessive loading or repetitive overuse, gradually the sheath becomes filled with inflammatory fluid or oedema, and this causes friction on the sliding tendon, making it feel sore and “gummed up”. This then inhibits free movement of the tendon and causes the feeling of being stuck, meaning the opposing muscle (antagonist) doesn’t have the strength to pull the knuckle back the other way.
The correct name for this condition is Stenosing Tenosynovitis (Stenosing meaning narrowing or constricting, tenosynovitis meaning inflamed tendon sheath). What actually happens is that a focal nodule or bump of swelling in the tendon is pulled under and behind one of the connective tissue “pulleys” that bind down the flexor tendons and allow manipulation of the fingers. As the tendon shortens the bump slides with it, and once it is stuck the tendon on the opposite side of the finger can’t produce enough force to passively slide the nodule back through the pulley. This causes pain and stiffness.
So what can we do to treat it? Initially we try conservative methods to reduce swelling and inflammation such as ice, non-steroidal anti-inflammatory drugs and massage, as well as stretching the associated muscles to relieve tightness. This can be coupled with electrotherapy such as ultrasound, and dry needling for better relief of spasm.
If these conservative methods fail then ultrasound-guided corticosteroid injection can dramatically reduce the swelling for 2-12 weeks, allowing rehabilitation exercise to continue more aggressively, so that the problem doesn’t return when the injection wears off.
Though this has been historically called Trigger Finger, I can imagine a future condition we will be diagnosing called “X-Box Thumb” or “Texting Thumb”!