Doctors cannot always identify the cause of tendonitis in the hand; however, when they can, the cause is often overuse and overload, says Drugs.com. Overuse is repeating a motion too often, and overload is doing an activity too excessively.
Tendonitis in the hand or wrist usually begins as an inflamed tendon, says Lehigh Valley Health Network. The irritated tendon may cause discomfort, pain and swelling. In a few rare cases, an infection causes tendonitis. There may also be a link between tendonitis and diabetes or rheumatoid arthritis. Some common types of tendonitis in the hand or wrist are De Quervain’s tendonitis, extensor tendon injuries, flexor tendon laceration and trigger finger.