Dear Welcome to HCM We understand your concerns Swelling on the knee joint could happen due to simple contusion or bruise, blocks in the blood veins carrying blood to leg (then swelling might also be available upto toes), or arthritis. You did not mention whether there is pain and burning sensation and did you use some home remedies or first aids like hot water fermentation. Just try to remember whether you had any impact there. If not, then consult a general physician for further advice. Get well soon.