Painful/swollen knee - pain/swelling now spreading to upper thigh also starting to affect other knee no injury-what could this be from?for months now

See below: It really could be any number of things from inflammatory (arthritis) to a ligamentous injury. I would start by seeing my pcp.

Many possibilities: The knee is an important weight bearing joint with a complex inner and outer structure. Your pain could be as a result of many different things. A thorough history and physical exam and possibly some laboratory and radiology exams are needed to determine the exact cause. Causes of pain may include: trauma (fracture, tendon or ligamentous tear, arthritis), infection, and metabolic conditions.