A carpal boss is a growth of extra bone on the back of the hand, where the long bones of the index and middle fingers meet the wrist. It shows as a firm, hard lump that does not move, and it is often confused with a ganglion. Most of the time it causes no pain and needs no treatment. In some people the tendons that straighten the fingers click or slide over the bump, or the small joint underneath becomes painful with wrist movement. Where that happens, a splint or an injection usually settles it, and where it does not, a short operation removes the extra bone and lets the tendons glide freely again.
What is a carpal boss?
The metacarpals, the long bones in the palm, meet the wrist bones at a row of small, stiff joints called the carpometacarpal joints. The ones at the base of the index and middle fingers barely move. A carpal boss is a bony overgrowth at the edge of one of these joints, where the base of the index or middle metacarpal meets the trapezoid or capitate. In some people it is a separate small bone, an os styloideum, that never joined the metacarpal. In others it is a spur that has formed at the edge of the joint over years of load.
The result is the same: a hard prominence on the back of the hand a couple of centimetres below the wrist crease, more obvious when the wrist is bent forward. Several of the tendons that straighten the wrist and fingers pass directly over it, which is where symptoms, when they occur, come from. It is also called a carpometacarpal boss.
Symptoms
Many people have no symptoms and find the lump by chance. Where symptoms occur, most people describe:
- A hard, fixed lump on the back of the hand at the base of the index or middle finger, more prominent when the wrist is flexed
- Aching over the lump after use, or with the wrist bent back under load, such as push-ups or pushing up from a chair
- Tenderness when the lump is pressed
- A click or snapping sensation as a tendon slips over the bump with wrist movement
- Occasionally a soft swelling next to the lump, which is a small ganglion arising from the irritated joint
The lump itself does not grow the way a ganglion can, and it does not spread.
Causes and risk factors
The cause lies in the development and loading of the joint rather than in anything you did. Contributing factors include:
An os styloideum, an extra small bone at the joint that is present from birth.
Wear at the joint. The index and middle carpometacarpal joints carry load every time you grip, and over time a spur forms at the edge of the joint in some people.
Repetitive loading of a bent back wrist, in some sports and trades.
Age. It is most often noticed between twenty and forty, and more often in the dominant hand.
How it is diagnosed
Mostly by examination. A carpal boss is hard, fixed to bone, and does not change size. A ganglion is softer, moves a little, often changes size from week to week, and lights up when a torch is held against it. The two can occur together, with a small ganglion sitting next to the boss, which is one reason a "ganglion" that is removed sometimes seems to come back. Our ganglion page covers that condition.
An X-ray confirms it. A standard view often misses a boss, so we ask for a lateral view with the hand tilted, which shows the prominence in profile. A CT scan shows the joint underneath in detail where surgery is being considered, and an ultrasound is useful where there is a question of a ganglion or of a tendon catching.
Non-surgical treatment
Where the lump is not painful, no treatment is needed. It is not dangerous, it does not turn into anything else, and it can be left alone. Where it is painful, most people settle without an operation.
Splinting and activity change
A wrist splint during aggravating activity rests the small joint under the boss and lets the irritation settle. Worn for a few weeks, it often settles a flare completely. Taking load off the bent back wrist helps: push-ups on the knuckles rather than the flat hand, and lifting with the wrist straight.
Hand therapy
Our therapists fit the splint, address the tendon irritation, and look at the way you load the wrist. Therapy is on site at Eastwood and at Morphett Vale, and starts the same week.
Corticosteroid injection
An injection into the small joint under the boss settles the inflammation, and it is diagnostic as well: if the pain goes, the joint was the source. We arrange these under ultrasound guidance rather than injecting in the rooms, because the joint is small and placing the steroid accurately matters. We would not repeat an injection more than twice at the same site.
Surgery
Surgery is for a boss that stays painful despite these measures, or where a tendon catches on it persistently. The aim is to remove the extra bone and allow the tendons to glide freely again.
The operation
Through a short incision on the back of the hand, the tendons are moved aside and the bony prominence is removed, down to and including the edge of the joint it arises from. Where the joint underneath is itself worn and is clearly the source of pain, that small joint is fused at the same time. Because the joint moves so little to begin with, fusing it costs no noticeable hand function. Whether a fusion is needed is decided from the imaging and from what we find at the operation, and we discuss it with you beforehand.
The skin is closed with sutures and a tape bandage covers them under a soft dressing, with a splint where the joint has been fused. It is a day procedure using sedation with a local anaesthetic, or a general anaesthetic where a fusion is planned, and takes about 30 to 45 minutes.
Recovery, week by week
Indicative, for removal of the boss alone. A fusion adds six weeks of splinting while the bone heals.
Day of surgery. The hand may feel numb or tingly for a day or two because of the local anaesthetic. Move your fingers for light tasks before you leave hospital.
Days 1 to 5. Keep the dressing clean and dry and the hand elevated. Finger movement from day one.
Days 5 to 14. The soft dressing comes off, leaving the tape bandage on the skin, which can get wet in the shower. Light use of the hand as comfort allows. A wrist splint is worn for comfort for the first two weeks.
Two weeks. Review by the doctor, hand therapist or practice nurse. Sutures are removed. Wrist movement exercises begin with your hand therapist.
Two to six weeks. The scar settles. Tenderness over the back of the hand is normal in this period and improves with massage and moisturiser. Loading the wrist, such as push-ups, is avoided.
Six weeks. Return to full use, including loaded wrist activity as comfort allows.
Driving and work. Driving and office work at four to five days. Light manual work at two to four weeks, heavy work at four to six weeks. After a fusion, heavy work waits until the bone has healed at about three months.
Risks and complications
Removal of a carpal boss is a small operation, and complications are uncommon. They can include:
Wound healing problems or infection. Usually superficial and treated with antibiotics.
Bleeding or bruising.
Nerve injury. Sensory branches of the radial nerve run across the back of the hand near the incision, and a patch of numbness or tingling, or a tender spot in the scar, can result.
Tendon irritation, where a tendon rubs on the cut edge of bone while it settles.
Ongoing tenderness over the scar, or slower than expected recovery.
Recurrence. The bone can regrow if the edge of the joint is not fully removed, which is why we take the prominence down to the joint.
Instability of the small joint if a lot of bone is removed, which can need a fusion later.
Where the joint is fused, the bone may be slow to heal, and a further procedure may be needed.
When to be seen sooner
Contact us, or see your GP, if you have:
- A lump on the back of the hand that is growing, or that is soft, warm or red
- A lump that appeared after an injury, where a fracture at the base of the metacarpal needs to be excluded
- Pain that is waking you at night
- A tendon that has started to catch or snap, or a finger that is harder to straighten
Almost every lump on the back of the hand is benign, and a carpal boss always is. If you have had surgery with us and have questions or concerns afterwards, phone the rooms during office hours on (08) 7127 0365.
Frequently asked questions
Is a carpal boss a ganglion?
No, although the two are confused all the time. A ganglion is a fluid-filled sac that is soft, moves, and changes size. A carpal boss is bone: hard, fixed and the same size every day. They can sit next to each other, and a small ganglion can arise from the irritated joint under a boss.
Is it dangerous or cancerous?
No. It is extra bone at the edge of a normal joint. It does not spread, does not turn into anything else and does not need removing to be safe. The only reasons to treat it are pain and a tendon catching.
Will it go away on its own?
The lump will not, because it is bone. The pain often does, with a splint and a period away from the activity that set it off.
Does removing it leave a dent?
No. The prominence is taken back to the level of the surrounding bone, so the back of the hand looks flatter rather than hollow. The scar is a short line on the back of the hand and fades over months.
Can it come back after surgery?
It can, if the edge of the joint is left behind, which is why the prominence is removed down to and including the joint margin rather than shaved off. Where the joint under the boss is worn and painful, fusing it at the same time removes both the source of pain and the chance of regrowth.
When can I drive and go back to work?
After removal of the boss alone, most people are driving and back at office work at four to five days, light manual work at two to four weeks and heavy work at four to six weeks. After a fusion, heavy work waits for the bone to heal at about three months. There is no legislation covering surgery and driving, so the test is whether you can control the car safely, including in an emergency. We will give you a realistic estimate for your job, and a certificate.
What does the surgery cost?
You will receive written informed financial consent setting out the surgeon, anaesthetist and hospital fees, your Medicare rebate and your health fund's contribution after your consultation and before anything is booked. Phone the rooms on (08) 7127 0365 if you have questions.
Do I need a referral?
Yes, for a consultation with one of our surgeons: a referral from your GP or another specialist. No referral is needed to see our hand therapists.
Written and clinically reviewed by Dr Paul van Minnen, MD, PhD, EBOPRAS, FRACS (Plast)
Last reviewed 8 November 2026