Trigger Finger (Stenosing Tenosynovitis)
Trigger Finger, or Stenosing Tenosynovitis, is a condition that affects the fingers and thumb, where a snapping or locking of the digits occurs when the hand is opened or closed. It is caused by an irritation of the flexor tendons of the hand, which are the tendons responsible for closing the hand or making a fist. Irritation, typically due to repetitive trauma or an inflammatory disorder (e.g. Rheumatoid Arthritis), causes the tendons to become swollen and enlarged and/or causes nodules to form on the tendon. This altered diameter makes it difficult for the tendons to travel through their tendon sheaths (the layer of membrane that surrounds each tendon) causing the tendon to become momentarily stuck at the mouth of the tendon sheath followed by a snap and a sudden straightening of the finger as the tendon slips through the tight area.