Bony bumps in the finger joints can be caused by excessive weight loss, which is normal. Secondly, there are also other diseases such as arthritis, tendon sheath cysts, or joint dislocation. 1. Normal: If you are too thin and have too little body fat, your bones and joints will be more pronounced, resulting in bulging of the bones in the finger joints. 2. Arthritis: Arthritis is a general term for various types of inflammatory diseases of the joints, the cause of which is related to degenerative diseases, autoimmunity and other factors. Patients will experience joint pain, swelling, stiffness and other symptoms, which can also lead to finger joint bone bulging. 3. Tendon sheath cysts: Tendon sheath cysts are benign cysts near joints, ligaments or tendons. The cause of the disease is not yet clear, but it is mostly related to degeneration of the joints, long-term injuries and other factors. Tendon sheath cysts may appear as superficial hemispherical bulges under the skin, and if the tendon sheath cysts grow in the joints of the fingers, they will cause the bones of the finger joints to bulge. 4. Other diseases: such as joint dislocation, gout, rheumatoid arthritis, etc., will lead to deformity of the finger joints, appearing finger joints bone bumps. For people with bulging finger joints, if accompanied by other discomforts, they should consult a doctor in time for a clear diagnosis and follow the doctor’s instructions for treatment.