Consider joint strain, tenosynovitis, gout, osteoarthritis, rheumatoid arthritis and so on. 1. Joint strain: If you often use your thumb, flexion and extension activities are too much, can cause joint strain, rest can reduce. 2. Tenosynovitis: thickening of the tendon sheath when the activity of the thumb pain, popping. 3. Gout: acute pain, accompanied by redness, swelling and fever, laboratory tests of uric acid can be clearly diagnosed. 4. Osteoarthritis: joint hyperplasia, articular cartilage wear and tear can cause pain at the root of the thumb, X-ray film can be a clear diagnosis. 5. Rheumatoid arthritis: symmetrical swelling of joints, pain, morning stiffness, rheumatism four tests, blood sedimentation can be clearly diagnosed. If the pain in the inner side of the thumb does not get better after resting, go to the hospital for examination.