Carpometacarpal bossing

Carpometacarpal bossing (CMC bossing) is a medical condition characterized by a bony overgrowth or prominence located at the back of the hand, near the base of the index finger and thumb. This condition is also commonly referred to as a "boss." It occurs at the carpometacarpal (CMC) joint, where the carpal bones of the wrist meet the first bones (metacarpals) of the hand. CMC bossing is often mistaken for ganglion cysts, but unlike cysts, the bossing is solid and does not fluctuate in size.

Causes and Risk Factors

The exact cause of CMC bossing is not well understood, but it is believed to be related to osteoarthritis or repetitive stress injuries. Individuals who engage in activities that place excessive stress on the wrist and hand, such as manual laborers or athletes, may be at higher risk. Genetic predisposition may also play a role in the development of this condition.

Symptoms

Symptoms of CMC bossing may include:

• Visible bump on the back of the hand
• Pain or discomfort in the wrist or hand, especially with movement
• Reduced range of motion in the affected joint
• Swelling or tenderness around the bump

Diagnosis

Diagnosis of CMC bossing typically involves a physical examination and medical history review. Imaging tests, such as X-rays or MRI, may be used to confirm the diagnosis and rule out other conditions, such as fractures or arthritis.

Treatment

Treatment for CMC bossing varies depending on the severity of symptoms. Non-surgical options may include:

• Rest and activity modification to reduce stress on the hand and wrist
• Ice and anti-inflammatory medications to manage pain and swelling
• Physical therapy to improve range of motion and strength
• Corticosteroid injections to reduce inflammation

In cases where non-surgical treatments do not provide relief, surgery may be considered to remove the bony prominence and alleviate symptoms.

Prevention

Preventive measures for CMC bossing are not well established due to the unclear causes. However, avoiding repetitive stress on the hand and wrist and using protective gear during activities that strain these areas may help reduce the risk.

See Also

• Osteoarthritis
• Repetitive Strain Injury
• Ganglion Cyst

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Carpometacarpal_bossing

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  Metacarpal boss
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  3D model of carpal boss
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  Hand of embryo
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  Bones of the left hand. Dorsal surface.
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  Bones of the left hand. Palmar surface.
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  X-ray of carpal boss
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  CT scan of carpal boss, sagittal view