Hii , Welcome To HCM & Thanks For Asking Your Query Here As You Did not tell about your age and sex , in elderly people Osteoarthritis is most common cause of knee pain. there may also a minor injury like twisting , sprain or strain , Apart from this there are variety of medical conditions which may cause a Knee Pain but seriously it needs thorough medical check up and investigations to spot a confirm diagnosis Your knee pain may or may not be related to your previous knee surgery however Anti inflammatory medicines like ibuprofen and muscle relaxant like thiocholchicoside along with rest and heat packs can give you relief from knee pain but still You should visit Your Doctor for this, he will examine it and will probably do An X ray of knee joint and CT scan If required so finally i would strongly suggest you to see a Orthopedic Surgeon to rule out any underlying medical condition I hope it help Thanks & Get well Soon