Causes

Tendons are fibrous cords that attach muscle to bone. Each tendon is surrounded by a protective sheath. Trigger finger occurs when the affected finger's tendon sheath becomes irritated and inflamed. This interferes with the normal gliding motion of the tendon through the sheath.

Prolonged irritation of the tendon sheath can produce scarring, thickening and the formation of bumps (nodules) in the tendon that impede the tendon's motion even more.