The Repair That Fails Quietly, by a Few Degrees at a Time
The tendons on the back of your hand and fingers straighten them. Cut one and it gets repaired, and the recovery looks nothing like a flexor tendon repair, even though people assume it’s the mirror image.
Flexor repairs fail loudly. The tendon ruptures and the finger stops bending.
Extensor repairs usually fail quietly, as a lag. The finger bends fine, looks fine, works fine…and just doesn’t quite straighten all the way. Ten degrees. Then twenty.
Nobody notices it happening, which is exactly the problem.
What’s actually happening in there
Flexor tendons are thick round cords. Extensor tendons are thin flat ribbons, sitting directly under the skin with almost nothing between them and the bone underneath.
Two consequences follow from that, and they run in opposite directions.
First, there’s less tendon to stitch into. An extensor repair holds less well than a flexor repair of the same quality, so it needs protecting.
Second, a flat ribbon lying against bone with barely any tissue between them sticks to that bone readily. Protect it too well and it scars down flat, and a tendon glued to bone can’t slide.
Then there’s the geometry. Extensor tendons have very little slack in the system. A repair that heals even a few millimetres longer than it started…because it stretched slightly, or a stitch loosened, or scar filled a gap…costs you degrees of straightening permanently.
There’s just no margins, space or reserve to absorb it.
(That’s the extensor lag. Not a failure of effort. A few millimetres of length, converted into a finger that won’t flatten on a table.)
Where the cut was changes everything
Extensor injuries get grouped by level, and the level dictates the plan.
- Over the fingertip joint: that’s mallet finger, usually splinted rather than stitched.
- Over the middle knuckle: the central slip, and the risk of boutonnière deformity if it isn’t handled properly.
- Over the back of the hand and the big knuckles: the classic repair territory, and the zone that responds well to modern early-motion splinting.
- At the wrist and forearm: multiple tendons in tight compartments, higher adhesion risk, longer rehab.
Ask which zone yours was. Two people with “an extensor tendon repair” can be on completely different protocols and both be correct.
What treatment actually looks like
The old approach was straightforward: splint everything straight for weeks, protect the repair completely, then start moving. It protected the repair well and produced a lot of stiff fingers.
Modern practice for many of these leans on controlled early motion instead, and one splinting idea in particular is worth understanding because it looks strange.
A relative motion splint holds the repaired finger’s big knuckle slightly HIGHER than its neighbours…a small yoke across the back of the hand, nothing else. That tiny difference in position takes tension off the repaired tendon while letting you use the hand almost normally.
It looks far too casual for someone who’s just had a tendon repaired. It works because the mechanics are doing the protecting rather than the immobilisation.
A flexor repair is protected by holding still. An extensor repair is protected by position, so it can keep moving.
Which splint you get depends on the zone and the surgeon. What doesn’t vary: it goes on early, it stays on, and the exercises get done daily.
What recovery feels like
- Weeks 0 to 4: splinted, controlled movement per protocol, swelling managed. Wound care and elevation.
- Weeks 4 to 6: splint weaning begins. This is when any lag becomes visible, and it’s the point to escalate rather than accept.
- Weeks 6 to 8: active straightening work, scar management, light functional use. Still no resistance.
- Weeks 8 to 12: strengthening. Gripping returns.
- Months 3 to 6: full use. Scar softens, remaining stiffness slowly improves.
The thing to watch for, weekly: lay the hand flat on a table and see whether that finger goes down as flat as its neighbours. A gap that’s growing rather than shrinking between weeks 4 and 8 is the signal to get seen, not to wait for the next scheduled appointment.
The short version
Extensor repairs don’t usually snap. They stretch and stick, and the finger loses a few degrees of straightening that it doesn’t give back.
Ask which zone you had. Wear the splint exactly as fitted, even if it looks like it’s barely doing anything. And check the hand flat on the table every week…that’s the whole early-warning system.
Written by Nigel Chua, hand occupational therapist in practice since 2005. Tens of thousands of hands, wrists and elbows assessed and treated. My credentials are here. This article explains; it doesn’t examine. Follow your own surgeon’s and therapist’s protocol over anything here.