A carpal boss, which is short for carpometacarpal boss, is an overgrowth of bone where your index or middle finger meets the carpal bones. Your carpal bones are eight small bones that make up your wrist. The condition is sometimes called carpal bossing.

This overgrowth causes a firm lump on the back of your wrist that doesn’t move. Most people with a carpal boss don’t have any symptoms. The condition only requires treatment if it becomes painful or starts to limit the range of motion in your wrist.

Read on to learn more about carpal bossing, including what causes it and available treatments.

The main symptom of a carpal boss is a firm lump on the back of your wrist. You can have it in either one or both wrists.

Most people don’t have any other symptoms. However, sometimes the bump becomes tender to the touch or painful when you move your wrist. Some people also experience painful snapping of nearby tendons when they move over the bony lump.

Researchers believe these symptoms might be a result of another underlying condition, such as:

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Experts aren’t sure about the exact cause of carpal bossing. For some people, it seems to be related to a traumatic injury or repetitive wrist motions, such as those involved in racket sports or golf. In addition, it tends to affect your dominant hand, further suggesting that repetitive motions and overuse may play a role.

For others, it might also be a congenital condition caused by bone spurs that form before you’re born.

To diagnose carpal boss, your doctor will likely start by asking a few questions to determine:

  • when you first noticed the lump
  • how long you’ve been having symptoms
  • what movements, if any, bring on or worsen your symptoms
  • how your symptoms impact your daily activities

Next, they may examine your wrist and try moving your hands in different directions to test your range of motion. They may also feel the bump to check if it’s hard or soft. This helps to differentiate carpal boss from a ganglion cyst. These cysts look similar to carpal boss, but they’re filled with fluid and not as firm. However, sometimes a carpal boss can cause a ganglion cyst.

If you have a lot of pain, your doctor might also order an X-ray or MRI scan to get a better look at the bones and ligaments in your hand and wrist.

Carpal boss doesn’t require treatment if it doesn’t cause any symptoms. However, if you do have pain or tenderness, or the bump gets in the way of your daily activities, there are several treatment options.

Nonsurgical treatment

If you need treatment, your doctor will likely recommend starting with nonsurgical treatments such as:

  • wearing a splint or bandage to immobilize your wrist
  • taking over-the-counter pain medication, such as acetaminophen or ibuprofen
  • icing the affected area
  • injecting a corticosteroid into the lump

If you don’t notice an improvement in your symptoms within two months, your doctor may suggest surgery.

Surgery

Your doctor can surgically remove the bump. This is a very straightforward outpatient procedure that usually takes less than an hour to do. You’ll receive local anesthesia, regional, or general anesthesia before your doctor makes a small incision in the back of your hand. Next, they’ll insert surgical instruments through this incision to remove the bump.

Following surgery, you’ll likely be able to start using your hand within a week, and return to your usual activities within two to six weeks.

Some people require a second procedure after having a carpal boss removed. This procedure is called carpometacarpal arthrodesis. It involves removing damaged bone and cartilage to help stabilize your wrist. Depending on your symptoms, your doctor might recommend this procedure over just removing the carpal boss.

Unless you’re experiencing pain, a carpal boss doesn’t require any treatment. If you have concerns or are experiencing symptoms, talk to your doctor about your options. You can try nonsurgical treatments, which should provide relief within a month or two. Otherwise, your doctor can remove the carpal boss.