Moozer, welcome in, though being an impingement victim not an easy ride.
As regards your 'prehab' its good to have a strong core and glutes. A lot of the pilates based stuff can be good including working to strengthen your transversus abdominus.
Glute squeezes, bridges, i use 'tabletop' pilates move. I think a few planks do no harm.
After the injury which i eventually had diagnosed as FAI, I was not able to run as pain quickly increased but was able to exercise bike - i used a lot of this up to 2 weeks before op as i figured i wanted to keep weight down as wouldnt be doing any serious exercise for several months. Wasnt told to do this by anyone just did it myself. I stopped 2 weeks prior to op to minimize risk of colds/chest infections which might have postponed op - to this end i looked after myself well in the weeks running up to op didn't drink, ate well, drank vit C supplement to avoid colds etc.
Several months into having right hip pain which stopped me from running, i noticed some discomfort on my left. Like yourself, I was susequently diagnosed with both right and left FAI. The left is not quite asymptomatic but largely feels fairly normal, some twinges and sensations etc. This might change and get worse if i were to start running again in future. It might be that your good left was at brecking point, and overcompensation after the right 'went' has been the straw that breaks the camels back. I know that it is not uncommon for one hip to go first, followed relatively quickly by the other, as Pipes said. I also think that the pain is often quite vague, hard to pinpoint, and can even move between one hip and the other as one hip takes the strain, then the other, in a hip balancing act of stress and weight.
Well quick update about me, I will be 5 weeks post op in 2 days time.Last week wasn't great, I felt sore and inflamed along the right pubic line, i guess where the adductor longus and magnus joins the bone. 5 days it lasted until it calmed about 2 days ago. I think the combination of all the exercises i was doing and how often i was doing them was the main factor. So i increased anti-inflams to 3x400mg ibprofen, scaled back my exercises quite alot, and iced.
It has calmed a good bit. Saw physio today told her the story she agrees with scaling back to basics, she ultrasounds, massages, muscles in area were not tight apart from my quad a liitle, and she told me to take a day off from exercise here and there. Says its my body going 'enough for now'.
Improvements to my limp has stagnated. Physio says its difficult for me to build muscle strength to improve limp without inflaming everything else. Hey ho, a fine balancing act. I think a little bit less is more for me right now. She also said something about getting an MRI before she considers increasing rehab, i get reviewed by surgeon on 8 feb.
I am bored bored bored. GP gave me another week off work, in fact she told me to take 3! Too much. I miss going for long walks into town and jumping about to CDs in the house.