Knee pain when bent in a right angle. Also when lying flat with the knee straight

Hello Anon

Thank you for writing.

Unfortunately, we are not in a position to answer that question as you need further examination and testing. It's possible you have some kind of arthritic condition or damaged tissue surrounding the replacement. I assume you have no noticeable hip or back pain now? It's not likely you would have back or hip damage and only feel it in the knee.
Best,
Susan