I am 29 and in good health, but developed chronic pain and swelling in my left knee in June 2001. The initial onset occurred during dance practice one evening. I was a competitive ballroom dancer, practicing 10-15 hours a week, but there was no injury, impact or trauma at the time to cause the pain. I went though 2 rounds of physical therapy, including the Protonics device, between June and December with no lasting results. In December the right knee developed pain and swelling too, and I started a 3rd round of PT. By March I had so much swelling and pain in both knees that I ended up in a wheelchair (couldn't manage crutches until one knee calmed down enough). Blood test and x rays for arthritis were negative, and MRIs and physical exams showed no meniscus or ligament damage. After seeing 4 OS and 3 PTs in the state where I live, I flew downt to the Cincinnati Sports Medicine Clinic. Dr. Noyes was brilliant, pointing out that I had patellar tendonitis from "kissing knees" resulting from too much internal rotation in my femurs (congenital). With my degree of malalignment, flexion produced too much stress in my knee joints. I am very relieved to know that there is a biomechanical reason behind my pain - that it's not without cause or is "all in my head." Correcting this problem is problematic in itself, probably requiring femoral osteotomy in both legs, but at least I know the source of my pain and swelling. I do pt every day, wear braces to hold my patellas in place and have put my dancing on hold (just for now!!) to manage the swelling. It has yet to disappeared completely. I've had to go completely outside of my insurance's network of health care providers and have accrued thousands of dollars in medical bills just to get some answers, but for me it has been worth it. If anyone has similar experiences they can share, has had femoral osteotomy, or has found non-surgical means of remaining physically active, please post your thoughts. Best of luck to everyone in your search for answers. I wish you much success.