De Quervain’s tendinosis is a painful swelling (inflammation) of the tendons of the thumb. Tendons are bands of tissue that attach muscles to bones. Usually, tendons slide easily through a tunnel of tissue called a sheath. The sheath keeps the tendons in place next to the bones of the thumb. Tendons that easily slide through their sheaths allow the thumb to move without difficulty or pain. Any swelling of the tendons and/or thickening of the sheaths causes friction. The tendons can no longer easily slide through their sheaths. When this happens, certain thumb and wrist motions become more difficult to do.
The exact cause of de Quervain’s tendinosis is unknown. However, it can be triggered by several factors as follows:
- A direct blow to the thumb.
- Repetitive grasping.
- Inflammatory conditions (including arthritis)
- Women 8 to 10 times more often affected than men.