I had OATS in Oct 07 LK.  It was a very slow healing process but I don't recall going backwards with the pain.  However, I stressed both knees out bad in Jan/Feb09.  I never really got swollen as much as a little puffiness and tenderness, the knee felt warm to touch.  The OS would always ask if it swelled up, I think this may be a big problem they look for but mine did not.  I went to the OS on Feb 27, 2009, with great pain.  His concern was swelling, he did not take Xray's or have me go for MRI's.  I went to another OS who first thing took an Xray and I was sent for an MRI.  The MRI showed that the OATS plug did not take.  Perhaps this is what may have happened to you.  You may want to condier another OS, there's got to be a reason for your swelling and pain, why didn't your OS take more Xray's or send you for an MRI?  MRI is the only way of knowing if the OATS failed.  I hope you get a second opinion, good luck.