During my build up to ironman uk 2023, I developed an ache in my hip that would spread through my hip Flexor and up into my lower back. I’ve been to 3 physio’s and had an x Ray and mri scan on my hip which didn’t find anything wrong. So I’ve turned to chat gpt for answers 
and seem to be making progress. I mentioned to it that I didn’t suffer the same issue when riding indoors. So we’ve gone down a route of strengthening my hip stabiliser and seem to uncovered that my hip flexor is doing too much work in the down motion of my pedal stroke. I’m wondering if riding rollers instead of a static turbo would aid in activating my hips stabilisers when riding inside. Anyone else ever had this issue? After 3 years it’s driving me mad now
Have you had a bike fitting?
Second this. I’ve had osteoarthritis diagnosis in my hip. Proper bike fitting (including shortening my crank arm length) is what’s allowing me to keep riding comfortably.
Yes I’ve had a bike fit. It happens on all 3 of my bikes, road, tt and mountain bike. So quite different positions. I get similar ache driving also.