What happens at the pulley in trigger finger?
The flexor tendon runs through a tunnel held against the bone by pulleys. The first of them, the A1 pulley, sits at the knuckle in the palm. In trigger finger the tissue of tendon and pulley thickens there. The tendon no longer passes smoothly through the narrow point and catches.
The pulleys are retaining loops. They press the flexor tendon against the bone as you make a fist, so it does not lift away from the hand like a bowstring. Each long finger has five of them. The A1 pulley is the first and lies closest to the body, right in the palm over the knuckle.
Under sustained load the tissue at that point remodels. The pulley grows thicker and firmer, and the tendon thickens at the rubbing point into a nodule you can feel. Under the microscope the change goes towards fibrocartilage, so less a classic inflammation than a remodelling under pressure.
The old name Tendovaginitis stenosans means literally «narrowing inflammation of the tendon sheath» and therefore misleads. Anyone who suspects an inflammation waits for it to settle and is surprised that resting alone changes nothing. The narrow point is a mechanical mismatch: the nodule has grown too thick for the tunnel.
Why does the finger snap and stay caught in the morning?
The thickened part of the tendon slips under the pulley as you bend and gets stuck in front of it as you straighten. Only more force pushes it through, and that is the snap. The common explanation for the morning being worst is that the hand barely moves overnight, tissue fluid gathers and the nodule swells. That has not been cleanly studied.
Bending is usually easier than straightening. The flexor muscle is strong and pulls the nodule under the pulley. Straightening uses the weaker extensor tendons against the same narrow point, and the nodule stays in front of it. That is why the finger sticks bent and not straight.
- At the start there is often only tenderness in the palm over the knuckle, without any snapping.
- Then the snapping arrives, at first now and then, later with every fist.
- At the next stage the finger can only be straightened with the other hand.
- Finally it stays bent and can no longer be straightened even passively.
Why the symptoms are worst in the morning has not been settled. The common explanation runs: overnight the hand lies still, fluid gathers in the tissue, and the nodule swells so that it passes even less well. After a few movements the block often frees up for the rest of the day.
Many people feel the pain not where the problem sits but at the middle joint of the finger. That regularly leads to confusion with finger osteoarthritis. A look at the palm helps: if there is a tender nodule over the knuckle, that speaks for the narrowed pulley.
Which fingers are affected and who gets a narrowed pulley?
Most often it is the ring finger, thumb and middle finger, usually on the working hand, often from middle age and in women more often than in men. About two to three in a hundred adults are affected in the course of their lives. With diabetes and inflammatory rheumatic disease it occurs considerably more often.
Manual work alone does not explain the condition. Tasks with long, firm gripping around hard handles load the site, but most of those affected have no such job. The disposition of the tissue weighs more than the occupation.
- Diabetes mellitus: clearly raised risk, often several fingers on both hands and more stubborn courses.
- Inflammatory rheumatic disease, such as rheumatoid arthritis (fremde Seite, öffnet in einem neuen Fenster): the tendon sheaths are involved anyway, so the narrowing arises more easily.
- Gout and thyroid disease occur more often among those affected.
- Carpal tunnel syndrome or Dupuytren’s contracture in the same hand is not rare; the tissues react in similar ways.
With diabetes it is worth knowing about this link, because it orders your expectations. Measures short of surgery take longer there, several fingers one after another are the rule and not a sign of failed treatment, and keeping an eye on blood sugar control helps the hand along.
What does a splint do for trigger finger?
A splint blocks one finger joint and so shortens the distance the thickened part travels under the pulley. It is usually worn for six to ten weeks, mainly at night. The success figures in studies range from just under half to over ninety per cent; the studies are small and built differently.
The thinking behind it is mechanical. If the knuckle is held in only minimal flexion, the nodule barely slips under the pulley any more. If the middle joint is blocked instead, the knuckle stays free but the travel of the deep flexor tendon is also shortened. Both versions are in use; which one fits depends on the findings.
- The splint sits at one joint only. The other fingers and the wrist stay free, otherwise the whole hand stiffens.
- It is worn mainly at night, because that is when the block builds. During the day it depends on symptoms and tasks.
- Six weeks is the usual first attempt. If things improve slowly, it is extended up to ten weeks.
- Without movement exercises in between the finger goes stiff. The splint does not replace the practice.
The evidence is thin. The range from just under fifty to over ninety per cent says above all how differently the studies were built: small groups, different splints and wearing times. A randomised study found no difference after one year between splint alone, injection alone and the two together.
That is no reason to leave the splint out, but a reason for a sober order of steps. The splint carries little risk and keeps every further option open. It works best early, while the finger only snaps and does not lock. After about ten weeks without change the attempt is over and the next step is due.
How often does a steroid injection help?
With an injection the doctor puts a steroid preparation into the tendon sheath over the pulley. Figures for how well the first injection works range from about 45 to 80 per cent. Second and third injections work less often and for less time. The longer the symptoms have lasted, the poorer the prospect.
Steroid reduces the swelling in the tissue around the narrow point. If the nodule gets smaller, it passes again. That explains why the effect often sets in within days to weeks, and why it turns out better with a short history than with a finger that has been locked for a year.
- The effect lasts about a year in some people; in others it never comes.
- At most two to three injections at the same site are usual. After that surgery is the more likely step.
- Possible side effects are a dimple or lightening of the skin at the puncture site, a short flare of pain in the first days, and rarely an infection.
- With diabetes the blood sugar can rise for a few days. That belongs in the conversation before injecting.
- Between an injection and an operation at the same site an interval of about three months is kept, because the risk of infection otherwise rises.
The wide range of success figures has a reason: the studies count differently. Some treat relief of pain as a success, others only the complete disappearance of the snapping over years. Anyone hearing a percentage should ask what counted as success in it and over what period.
The injection does not replace occupational therapy, it makes room for it. While the swelling is down, tendon gliding exercises, the splint and the step-by-step build-up of load can be done with little pain in the first place. Carrying on with both holds the result of the injection considerably longer, in our experience, than letting everything rest once the pain has eased.
When is the pulley released and how does it go afterwards?
Releasing the pulley is due when the finger stays locked for good, or when splint and injection no longer hold. Through a small cut in the palm the A1 pulley is divided, usually as a day case under local anaesthetic. You may move the finger at once, and the stitches come out after ten to fourteen days.
The drawing shows why it is the first pulley of all that is divided. Five pulleys hold the flexor tendon against the bone along the whole length of the finger; from the palm to the fingertip they are called A1 to A5. Without them the tendon would lift away from the bones like a bowstring as you bend. A1 sits at the level of the knuckle, exactly where the thickened part of the tendon has to pass. The other four stay untouched, and the tendon is still guided.
The operation removes the narrow point and not the nodule. Because the first pulley can be spared for guiding the tendon, strength is preserved. Open release counts as the reliable route; it is often carried out under an anaesthetic that lets you move the finger yourself on the table, and the snapping disappears at once.
- Day of the operation: a small cut in the palm, a dressing. The finger may be moved actively at once.
- Day 3 to 5: dressing off, the hand may be washed with water and soap.
- Day 10 to 14: stitches out. Scar treatment starts after that.
- Week 2 to 4: everyday grips without force, no firm gripping, nothing heavy to carry.
- Week 4 to 6: building strength and returning step by step to all activities.
Serious complications are rare and in the order of under five per cent: injury to a finger nerve, infection, the tendon lifting away from the hand as you bend. More common and more harmless is a scar in the palm that stays tender for weeks when pushing up and when holding a tool.
Anyone who has lived a long time with a locked finger often has a straightening deficit at the middle joint that remains after the release. That is the real reason not to wait indefinitely. How the weeks afterwards go is set out at greater length in hand therapy after surgery.
What does occupational therapy do for trigger finger?
Occupational therapy makes the splint, practises the tendon gliding, treats swelling and scar, and works on the movement lost after weeks of sparing the hand. To that comes a look at daily life: which grips irritate the hand and which tools put less pressure on the palm.
Before an operation two things matter: taking load off the narrow point and keeping the finger moving. The splint is shaped on your finger and readjusted if it presses or slips, because a splint that lies in a drawer because it fits badly does nothing.
In tendon gliding the hand runs through several fist shapes that move the superficial and the deep flexor tendon against each other. That keeps the tendons gliding against their surroundings. Practise slowly and without force, briefly several times a day rather than once at length. Forcing the locked finger straight is not part of it.
- Flat hand: all fingers straight, the starting position.
- Hook fist: knuckles straight, middle and end joints bent.
- Half fist: knuckles and middle joints bent, end joints straight.
- Full fist: all joints bent, without help from the other hand.
After the release, swelling and scar come first, then the movement. The hand is kept raised and moved regularly, and once the wound has healed the scar is cared for and shifted carefully against the layer beneath. A stiff middle joint takes longest, and it is the reason the aftercare rarely ends when the stitches come out.
In hand therapy we also look at what daily life asks of the hand: secateurs, bicycle grips, tools, shopping bags carried on the fingers instead of the forearm. With a doctor’s prescription you can book an appointment; it is billed to the insurer responsible.