Just saw the doctor and the X-rays. The cause of my knee issue is pretty much what I thought. I have a protrusion on the outer backside edge at approximately 6 o'clock on my kneecap. The doctor believes that it is settling in the "fork" at the bottom of the prosthetic when my knee is bent. When I straighten my leg, it hangs up until at some point it lets go. You can actually see it happen. He said he has never seen this before.
Anyway, the solution is to go back in and remove the protrusion. While it could happen, he doesn't think it would come back. He doesn't believe it can be done arthroscopically. Ugh! I am on the waiting list for surgery. Again.