Warts, tendon cysts, gout, arthritis, bone tumors or soft tissue tumors may be the cause of a hard bump on the index finger joint. 1. Warts: a kind of skin surface superfluous organisms caused by human papilloma virus infection of the skin, patients can appear index finger joints bulging a hard lump. 2. Tendon sheath cysts: chronic aseptic inflammation due to repeated wear and tear of the tendon sheath of the finger joints. 3. Gout: due to various causes of gout stone accumulation in the joints of the index finger, the patient may also appear the phenomenon. 4. Arthritis: commonly seen in rheumatoid arthritis, the active phase can produce rheumatoid nodules and finger swelling and other symptoms. 5. Bone tumors or soft tissue tumors: due to abnormal proliferation caused by bone tumors or soft tissue tumors, patients may also experience this phenomenon. Index finger joints drum a hard lump may also have other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, give targeted treatment or treatment.