Sudden and unexplained swelling and pain in the wrist is related to arthritis, tendon sheath cyst, rheumatism and gout. 1. Arthritis: after catching a cold or exertion can lead to an acute attack of arthritis symptoms, causing pain or swelling of the wrist joint, especially the elderly are prone to. 2. Tenosynovitis: prolonged fatigue of the wrist, such as long-term use of the mouse or keyboard and other chronic strain on the wrist, can induce tenosynovitis, swelling and pain in the wrist. 3. Rheumatism: the human body in the body resistance to decline or the existence of immunodeficiency can be infected with streptococcus bacteria, resulting in the involvement of the wrist joint, swelling and pain. Rheumatoid arthritis can also be induced after attacking the bones, and the pain and swelling will be further aggravated, and some patients will also be accompanied by joint deformity. 4. Gout: the typical symptoms are sudden joint pain and swelling, many patients can wake up at night because of pain. Sudden and unexplained swelling and pain in the wrist may also be caused by other reasons, it is recommended to go to the hospital for relevant examinations, clear diagnosis and timely treatment.