What Is a Carpal Boss?

Carpal bossing is the name given to a bony lump on the back of the hand. The carpal boss is a bump occurring at the junction of the long hand bones and the small wrist bones.

A carpal boss is most commonly seen as a bump on the back of the hand at the middle or index carpometacarpal joint—where the hand bones meet up with the wrist bones. The word boss comes from the French word bosse, which means a bump or swelling.

Carpal bossing is due to bone growth at the base of the metacarpal bones of the hand. It must be differentiated from other, more common wrist conditions such as:

• Wrist ganglions
• Tendonitis
• Fracture

A carpal boss is not a cancer or a tumor. While there are very rare bone tumors that can occur in the hand, your healthcare provider should be able to differentiate a carpal boss from something more concerning.

Signs and Symptoms

Most patients complain of symptoms related to a carpal boss after they bump or hit against the back of the wrist. This type of trauma can cause irritation around the carpal boss. The tendons over the back of the hand can also become irritated because of the carpal bossing. Sometimes you may experience a tendon snapping as it moves over the bump. Lastly, some patients simply do not like the cosmetic appearance of the bump on their hand.

Your primary care healthcare provider may look further into the bump, or you may be referred to a hand specialist. If you are having pain and swelling, your healthcare provider will want to rule out other causes such as ganglion cyst, tendonitis, fracture, and less common causes of bumps on the wrist.

A physical exam, your history of when the bump appeared, and your symptoms are used to make the diagnosis. The tests that may be performed include X-rays as well as, depending on your symptoms, electromyography, which measures muscle response to nerve stimulation.

Treatment

Most often, carpal bossing is a problem that can simply be watched—with no specific treatment. Anti-inflammatory analgesics such as ibuprofen may be suggested if it is painful or inflamed. If it is painful, the healthcare provider may recommend a wrist splint to limit motion, or a steroid injection if that doesn't provide relief.

In cases where the condition is causing significant symptoms, a surgical procedure to remove the excess bone can be performed. It is usually done under local or regional anesthetic. It is a brief operation that is performed as a day surgery. An incision is made on the back of hand and the bump and any swollen tissue around it are removed. Depending on the extent of the surgery, typically you can use your hand for normal activity after a few days and return to work in a week or two.

Some surgeons will also fuse the bone at the joint where the spur is located to prevent a recurrence of the condition. There is conflicting literature as to how likely it may be that the bump returns after excision, but it is possible. However, excision has risks of joint instability as well as a common risk of infection and scarring.