Arthritis. Narrowing of the first mcp joint is usually due to some form of arthritis to the area. This may have several causes, as I would visit with my hand specialist or orthopedist before further narrowing or destruction occurs.
Arthritis. Narrowing of joint usually associated with cartilage damage and loss of height of articular cartilage. Could be traumatic or arthritic. If see narrowing on one side and opening up on opposite side with stress x-ray could indicate collateral ligament injury. Can see narrowing associated with fracture involving articular surface. See hand surgeon.