The following medical conditions are some of the possible causes of Knuckle swelling. There are likely to be other possible causes: Lymphedema Venous insufficiency Soft tissue injury Cellulitis Infection Blunt trauma Renal failure Heart failure Allergic reaction Insect bite Lymphadenopathy Venous thrombosis Medications Dermoid cyst Bone cyst Ganglion Knuckle injury Finger injury (type of Hand injury) Rheumatoid arthritis Septic arthritis. If you recognize arthritis symptoms in your hands and fingers, make an appointment with your doctor. They can teach you good joint exercises and help you find treatments that will ease the pain and discomfort you’re experiencing. So you better consult your family doctor or specialist for your problem.