The arrow in the picture points to the base of the 2nd metacarpal or 2nd carpometacarpal joint on the dorsum of the left hand. At this location, the most common causes of a painful lump or bump are:
- 2nd metacarpal bossing
- Synovitis of the insertion of the extensor carpi radialis longus tendon
- Synovitis of the extensor indicis communis or propius tendon to the index finger
A hand & wrist specialist will be able to clinch the diagnosis with a detailed clinical examination and imaging modalities such as X-rays, ultrasound or MRI scans. Early treatment will prevent the problem from becoming a chronic one, which may be trickier to treat.
