Stenosing tenosynovitis, commonly known as trigger finger, is a condition that affects the tendons and their surrounding sheaths in the fingers. Tendons function like ropes, connecting the muscles of the forearm to the bones in the fingers, enabling finger movement—particularly flexion.
These tendons run through a series of fibrous tunnels called sheaths, which act like pulleys. The sheaths keep the tendons aligned and close to the bone, allowing for efficient and controlled movement. Their inner surfaces are smooth and lubricated, permitting the tendons to glide freely during finger motion.
In trigger finger, inflammation or thickening of the tendon or sheath disrupts this smooth gliding motion, causing the finger to catch or lock during movement.