Swelling pain in the middle finger of the left hand can be caused by the following reasons: first, tenosynovitis, stenosing tenosynovitis patients can have swollen and painful finger joints, which can be accompanied by limited joint activity and morning stiffness, joints popping symptoms, severe cases will have obvious finger movement disorders, which should be diagnosed by early checkups, and early closed treatment, as well as oral medication, physiotherapy. Second, osteoarthritis, when the middle finger joints have degenerative osteoarthritis in old age, or secondary osteoarthritis caused by trauma, there can be swelling and pain in the finger joints, accompanied by the formation of bone cumbersome as well as finger movement limitation, this time, we need to check the finger joints of the X-ray film to diagnose and early treatment. Third, gout, when gout involves the finger joints, there can be finger joints of swelling and pain, can be accompanied by skin redness and swelling, as well as the formation of gout stone, this time to check the blood uric acid and take X-ray film to diagnose. Fourth, hand infection, when the finger joints or finger tips are infected, there can also be swelling and pain, can be accompanied by skin redness, this time to check the MRI and blood tests to diagnose.