You'll never really know without an MRI/scope, a lot of pains in the knee produce similar symptoms. Best to just go through the slow process of getting those if it doesn't get better over time/with physio.
Just had an arthroscopy on mine yesterday after almost a year of it giving me grief, the problem is the surgeon spoke to me after the procedure just as I was waking up from the GA and now I don't remember what he told me. The discharge letter simply says patellofemoral cartilage damage and nothing else - did they fix it? What next? Who knows!