I had a hip replacement in 2002. I have had pain in my upper thigh area ever since when I lift my leg

Have you talked to a doctor about this in the last ten years?

When you do a major surgery like that muscles and nerves are moved, stretched and readjusted with the hopes that you will heal that damage. You've had a major disturbance and a major injury, in your body's eye, done to you. Sometimes there are nerves and the like that have moved to a place where they're constantly firing.

That is the best I can honestly do here. You REALLLY need to talk to your doctor.