What are severe knee pain, swelling and tenderness possible symptoms of?

Non specific: Many things cause knee pain. For instance fracture, bruise, meniscus tear, inflammation, gout, rheumatoid arthritis, arthritis, ligament tear, effusion you need to see a doctor if it does not go away with routine Aspirin doses. To determine.... What is causing your pain. I do many mris to see whats wrong. However - just having pain in not enough to ask for an MRI - ask your doctor.