A condition usually occurring in middle-aged people in which the sufferer finds on wakening in the morning that he or she cannot straighten the ring or middle finger spontaneously, but only by a special effort, when it suddenly straightens with a painful click, hence the name. In due course the finger remains bent at all times unless a special effort is made to straighten it with the other hand. The condition is due to a swelling developing in one of the tendons of the affected finger. If the tendon sheath is slit open surgically, the condition is relieved. Many cases recover spontaneously if the patient is willing to wait.