The tendons that bend your fingers run through a tunnel or sheath. Sometimes the tendon can develop a thickened part which catches on the edge of the tunnel as the tendon glides in and out.
In later stages of trigger finger, the tendon can get stuck in the tunnel and the finger ‘locks’ down into a bent position
The treatment is usually a steroid injection, unless the patient has a locked trigger finger, in which case the injection may be unsuccessful. The success rate of an injection is around 60% unless the digit is a thumb or in diabetic patients. If the injection is ineffective, surgery may be offered.