Wrist tendonitis (also called wrist tendinopathy) is an inflammation or degeneration of any of the flexor or extensor tendons that cross the wrist joint. Biopsies have often found that inflammation is not part of this condition, and thus, tendinopathy is the more correct term for this condition (refers to degeneration of the tendon).
What causes it? This condition is due to overuse of the wrist due to repetitive friction or strain of the tendon. The tendon either rubs a bony prominence or is strained due to repetitive and excessive action.