Anyone who has a job that requires repeated hand motions is at risk for a variety of problems. One of the most common is tendinitis. Musicians are susceptible to a specific kind of tendinitis called de Quervain's disease.
When tendons are used repetitively or excessively, pain, swelling, and limited thumb motion can develop. With these come inflammation and an eventual thickening of the tendons and their coverings. This makes it even more difficult for the tendons to move.
For most people, anti-inflammatory medications, rest, and wearing a thumb splint help ease the symptoms. For musicians, these steps may take too long or interfere with work. An alternate form of treatment is the single injection of a steroid medication into the area. This allows the musician to return to work within three to five days.