Hi, I Had A L Total Hip Replacement June 2008.

Hi, I had a L total hip replacement June 2008. Been perfect until month or so ago. I get pain sitting from the butt bone up into the groin area / upper top of thigh on this L side. surgical approach was down outside of hip, as opposed to my R hip which was anterolateral. I notice if I sit on a low chair, then the pain is worse. Has been xrayed = no changes, but am wondering about the polyethylene liner. (It is a metal implant whereas the R hip is ceramic ball and titanium), and wear or migration which may not necessarily show on plain film.