Knuckles, Lumps or Tendons? The Back of the Hand Has Its Own Rules
Most pain on the top of the hand is overworked tendons, from gripping, typing or a new activity, and settles in days to a few weeks with less of the provoking load. A smooth lump that changes size is usually a ganglion. A hard bony bump that never moves is usually a carpal boss. After a punch, think fracture or a knuckle tendon that’s slipped. And a small cut over a knuckle from someone’s tooth, swelling up red and hot, is an infection that needs treating the same day.
The back of the hand gets ignored.
It doesn’t do the gripping, so when it aches, people keep going. When a lump appears, they wait to see if it goes. When they’ve split a knuckle on a night out…they stick a plaster on it and get on with their week.
Most of the time, fine. But the skin on the back of the hand is THIN. There’s very little between it and the tendons and joints underneath. Which is why a few back-of-hand problems go from small to serious much faster than they look.
Press around with one finger of your other hand until you find the worst spot. Then find it below.
First: the ones that don’t wait
- A small cut over a knuckle from punching someone’s mouth, now swollen, red or throbbing: a “fight bite”. Bites to the hand. Same day, and be honest with whoever treats you about how it happened
- A cut on the back of the hand, and now a finger won’t straighten on its own: an extensor tendon injury. Today
- Suddenly can’t lift the wrist or fingers, often after sleeping on the arm: a radial nerve palsy. Get it assessed, and keep the wrist supported in the meantime (wrist drop splint)
- Redness spreading up the hand or forearm, with fever: infection. Same day
A small cut over a knuckle from someone’s tooth is one of the most dangerous little wounds in the whole hand.
The tooth goes in with the fist clenched. Then you open your hand, the skin slides back…and seals the mouth bacteria in, right on top of the joint. It looks like nothing for a day. Tooth cuts over the knuckle should never be taped shut and ignored.
Over the knuckles
- After punching something solid, a knuckle has sunk or disappeared: a boxer’s fracture. Make a loose fist and check that finger doesn’t cross its neighbor
- The tendon over a knuckle flicks sideways into the gap when you make a fist: a sagittal band rupture, sometimes called boxer’s knuckle
- Knuckles puffy on BOTH hands, stiff for over an hour every morning: rheumatoid arthritis until a doctor says otherwise
- One knuckle suddenly hot, red and untouchable, often overnight: gout, or an infection. A first attack gets assessed
Rocky punched frozen sides of beef in a meat locker. Your knuckles are not Rocky’s knuckles…and neither, it turns out, were his.
The middle of the back of the hand
- A smooth, rubbery lump that gets bigger and smaller over weeks: a ganglion cyst. Usually harmless
- A hard, bony bump near the base of the index or middle finger bones that never changes: a carpal boss
- An ache along the tendon lines after a lot of typing, gripping or a new activity, worse when you straighten the fingers against resistance: overloaded extensor tendons. Desk work and general overuse
- A firm lump that’s slowly grown beside a finger tendon and doesn’t change size: possibly a giant cell tumor of the tendon sheath. Benign, but worth getting looked at
(Try this for the tendons: rest your palm flat on a table, then lift each finger off the table one at a time while your other hand gently presses down on it. Pain along the back of the hand on one tendon line…that’s the overloaded tendon.)
The thumb side of the back of the hand
- Pain just above the thumb base, worst lifting a kettle or a baby thumbs-up: De Quervain’s tenosynovitis
- Higher up the forearm, sometimes with a squeak: intersection syndrome
- Numbness or burning over the back of the thumb, often after a tight watch, cuff or handcuffs: Wartenberg’s syndrome
The whole back of the hand
- Puffy and stiff after a cast, splint or operation: the stiff hand after immobilization, and still swollen months after a wrist fracture
- Swelling, shiny skin, color or temperature changes and pain way out of proportion: CRPS. Today, not next month
- Burning or tingling rather than aching: a nerve. Burning hands and pins and needles: which nerve
Lumps that come and go are usually harmless. Cuts over a knuckle are not.
The short version
Achy tendon lines after a busy week: overload, ease off the provoking task. Soft lump that changes size: ganglion. Hard lump that never moves: carpal boss. Sunk knuckle after a punch: fracture, check for rotation. Cut knuckle from a tooth: same day, no exceptions.
Improving by day 7, let it finish. Same or worse at day 7, get it assessed. Pain more in the palm? Pain in the palm of the hand. In the fingers? Finger joint pain by location.
Not sure if yours is a “wait and see” or a “go now”? The Closing Window Chart just below maps 15 hand conditions: open, closing, shut, plus the red flags. One page, free.
Written by Nigel Chua, hand occupational therapist in practice since 2005. Thousands of hands, wrists and elbows assessed and treated. My credentials are here. Every article on this site is written using the Closing Window Method: name the window your condition runs on, find where you are in it, and act while it’s still open. This page narrows the field; it doesn’t examine you. Pain on the back of the hand that isn’t clearly improving by day 7 needs assessing.