I had exacted the same swollen and pain in the back of right knee then it creeps down to my calf, someday even my left calf aches. I finished 3-session of physical therapy. He sends me home with some stretch exercise. It seems help some. If it's the side effect from one of my meds. The pain could reoccur. I just keeping on stretching. Next follow up visit with an orthopedic not until September.