Common causes of metacarpophalangeal joint pain in the index finger include trauma, rheumatoid arthritis and stenosing tenosynovitis. 1. Trauma: there is a clear history of trauma, the muscles, tendons and ligaments around the index finger are damaged or even fractured due to violence, which can cause pain. 2. Rheumatoid arthritis: it is a kind of autoimmune disease that develops in women. Because of synovial inflammation, bone destruction and other reasons, causing finger pain, pain is mostly symmetrical. The pain is mostly symmetrical. In the early stage, it is mostly characterized by redness, swelling, heat pain and dysfunction of the finger joints, and pain in the metacarpophalangeal joints of the index finger can occur. 3. Stenosing tenosynovitis: also known as trigger finger, is a sterile inflammation that occurs in the tendon sheath, mostly caused by long-term strain. Although it occurs mostly in the thumb, it may also occur in the index finger. Common manifestations are popping pain in the fingers, difficulty in flexion and extension, and can present with pain in the metacarpophalangeal joint of the index finger. There are many causes of pain in the metacarpophalangeal joint of the index finger, and it may also be related to diseases such as chondroma, etc. If the symptoms continue to be unrelieved, it is recommended to consult a doctor in time to clarify the cause of the disease and carry out targeted treatment.