Trigger thumb is a condition wherein the thumb becomes painfully locked when bent, according to WebMD. It occurs due to the inflammation of the tendons in the thumb. Engaging in repetitive motions and using the thumb strenuously are common causes of trigger thumb.
Tendons are firm groups of tissue joining the bones and muscles, states WebMD. They work together with the muscles in the arms and hands to flex the thumbs and fingers. Tendons normally slide smoothly through their tissue coverings, known as sheaths, with the help of a lubricating membrane that surrounds the synovium joint. An inflamed tendon tends to break when the thumb is bent, pulling the tendon through a sheath that has become narrow due to inflammation or swelling.
Holding an object firmly for prolonged periods can lead to trigger thumb, says WebMD. Diabetes, gout and rheumatoid arthritis are medical conditions associated with a trigger thumb. Musicians, farmers and industrial workers typically experience trigger thumb because their jobs involve plenty of repetitive thumb movements. The condition typically happens in women and affects people between 40 and 60 years of age.
A sore thumb base is an early symptom of trigger thumb, notes WebMD. Other symptoms include a painful clicking sensation whenever the thumb is bent and a locked bent or straight thumb position that requires gentle adjustment using the other unaffected hand.