Hi there. 7 years now since THR anterior approach. I have had patches of time where I would get anterior hip pain with also low back and lateral knee pain at 3-5 mile point. I thought I maybe had done something to the hip or tore soft tissue but MRI was negative. Saw PT and was told I had gluteus medius weakness and doubled down on core work (bridges, resisted adduction, single leg squats) and I’m back in business. I think we all become biomechanically unbalanced due to the initial arthritis and then the prosthetic (lost proprioception) and get what they call “dead butt”. I hope that’s the answer for you. See a PT soon and at least get evaluated.