The first joint pain of the thumb is considered to be related to trauma, tenosynovitis, gouty arthritis, rheumatoid arthritis and other causes. 1. Trauma: If the thumb is hit by external force or injured during exercise, the symptoms of pain in the first joint of the thumb will appear due to injury of the tendon and soft tissue of the thumb. 2. Tenosynovitis: caused by frequent extension and flexion activities of the thumb, such as frequent use of cell phones, etc., which will cause frequent friction of the tendon in the tendon sheath, causing aseptic inflammation over time, resulting in pain in the first joint of the thumb. 3. Gouty arthritis: is caused by purine metabolism disorder, the patient will appear uric acid concentration is too high, when the urate crystals deposited in the joints and the surrounding soft tissues, will also cause inflammatory reaction, resulting in the first joint pain in the thumb. 4. Rheumatoid arthritis: an autoimmune disease, mainly characterized by erosive synovitis, and mainly involved in the small joints of the limbs, so it will also cause the first joint pain in the thumb, and there will be finger deformities, restricted movement and other symptoms. It can be seen that the causes of the first joint pain of the thumb are more, including bone tumor of the thumb and intra-articular fracture, etc. If the pain is severe, or accompanied by redness, swelling and fever, etc., you should go to the hospital for further diagnosis and treatment in a timely manner.