The carpal boss is a hypertrophied bony protuberance on the dorsal surfaces of the base of the second or third metacarpals, near the capitate and trapezium. It may be bilateral.
The condition may represent one or more of:
- degenerative osteophyte formation
- os styloideum (an accessory ossicle of the wrist)
- bony prominence at the base of the second or third metacarpals (which is often called "styloid process")
The radiographic appearance of a carpal boss is characteristic, however optimal visualization of the boss may be difficult to obtain due to superimposed bony structures.
CT may show degenerative disease at a pseudoarthrosis, and MRI may show edema related to abnormal motion.