Swelling and pain in the finger joints are most often caused by arthritis. Arthritis is caused by local blood circulation disorders caused by frequent contact with cold objects or cold water in the hands, and by inflammatory reactions in the joints caused by cold and moist external stimuli. Patients with arthritis of the finger may experience significant swelling and pain in the joint, which may be more pronounced when the joint is pressed, and sometimes the joint may feel stiff in the morning. Tendonitis can also be caused by labor injuries. People who work with their fingers frequently use them repeatedly for mechanical movements, which can cause the tendons and tendon sheaths near the joints to rub together repeatedly, resulting in inflammation and even narrowing of the tendon sheaths, resulting in tendonitis. This disease causes significant pain when bending the knuckles and swelling around the inflammation.