Hi Keith,
I mentioned this in some of my post this last spring/early summer. I had a very similar, weird experience. I had my sx June 2, 2010, and recovered well. I was riding horses fairly pain free three months postop. All last fall and early winter, I had no problems and I was increasingly getting stronger, more comfortable. All seemed well.
Then came mid winter (I think it was about early Jan.). Suddenly, I had quite a bit of pain, (very much like pre-op) and was limping again! I called the Dr. and made an appt for an exam. Radiographs showed nothing. Palpations, nothing.They told me not to panic and take NSAIDS as needed. I panicked. I worried. I even cried a little. I was sure it was failing! ( I could think of nothing I had done to cause this!) I even quit posting here for awhile, I didn't want to "bum" anyone out.
Then almost magically, it became better again. And, by the way, in case you're thinking it must have just been Oregon's cold, damp weather... the weather does not get warm and dry here until late June!! Especially this year. (this is only a slight exaggeration!)
The Dr's were right, probably just some inflammation and "healing pains". I have not felt it since. As a matter of fact, by the time my 1 year anniversary this June rolled around, it just kept getting stronger and better!
I hope this will be true for you, too. Of course Pat is correct, please go see your Dr. and make sure. Good Luck, Luann