@RaphPalo - so sorry to hear about your situation. I, too, had terrible groin pain for 2 years post op every time I needed to lift my leg. I couldn't get into car or bed or lift my leg up on a chair to tie my shoes without using my arms to assist the leg. They suspected cup overhang but imaging showed everything looked normal, other than what looked like mild inflammation in the hip flexor (iliopsoas) tendon. They said that even though cup overhang wasn't visible, there was a possibility I could have slight overhang that imaging wasn't picking up. But that was just a guess.
During my replacement surgery, I had a slight fracture in my femur which was fixed with a cerclage wire by my surgeon, so we thought another reason for my pain may be that the trauma to the femur bone weakened other muscles more than usual, putting more strain on that tendon in the groin. There was no question that my quads and glutes on the operated side were terribly weakened after the surgery and I was having trouble strengthening them because of the groin pain. No one could give me definitive answers and nothing worked. I tried everything, rest, targeted PT, acupuncture. AFter about a year, I saw 2 surgeons (one at HSS) who said the only thing they could suggest was tendon release, which would trade pain for some weakness. This was NOT something I wanted to do since they couldn't tell me me for sure what the heck was going on with that tendon.
I ended up reading in a forum somewhere - perhaps it was here at bonesmart, that someone with a similar issue started doing water therapy. That was one thing I hadn't tried, so I signed up at the YMCA and started swimming laps - slow and limited at first. After about 3 months I was swimming twice a week, about 25 laps. My groin started feeling a little better! Then I switched to a water aerobics class. I also did stretches on my own in the pool after class was over. I was able to move my leg / body in the water in ways that I couldn't on land. About 3-4 months after that, my pain was 100% gone! I think I just needed to increase my mobility and strengthen areas around the hip that I simply wasn't able to do on land because of the tendon pain I would experience while trying.
If you are sure you have cup overhang, which sounds like the case - I would ask the surgeons (definitely get more than one opinion) on the pros/cons of both tendon release AND revision surgery in such a situation. Also, is the overhang just slight, and if so, would that make a difference in pros and cons of each. I was afraid of the "trading pain for weakness" effect of a tendon release, but I have read accounts of some who after exercise and strengthening only had very minimal or no issues with weakness. The consensus may be that a revision is what's best for your situation, but I'd still ask the question about a release as an option. Either way, it sounds like you are on your way to getting this fixed one way or the other. Revisions have also been very successful from what I've read. Best of luck to you - you'll get there!!! Keep us posted.