Swelling and pain in the thumb may be caused by trauma, tenosynovitis, arthritis, gout and other reasons. 1. Trauma: When the thumb is injured by external force such as impact, it may cause soft tissue injury or fracture, causing swelling and pain in the thumb. 2. Tenosynovitis: strain, trauma, infection and other factors may lead to tenosynovitis. Patients suffering from tenosynovitis may experience symptoms such as swelling and pain in the thumb, and restriction of joint movement. 3. Arthritis: rheumatoid arthritis, rheumatoid arthritis, osteoarthritis and other diseases may cause swelling and pain in the thumb. 4. Gout: gout is a purine metabolism disorder or uric acid excretion disorder caused by metabolic diseases, patients suffering from gout, may be due to the accumulation of uric acid caused by thumb swelling and pain. In addition, hemangioma, carpal tunnel syndrome and other causes may also lead to thumb swelling and pain, the symptoms of thumb swelling and pain, should be timely to the hospital, to identify the cause, symptomatic treatment.