hip pain

my son was hit by a car 2 months ago with no apparent leg injury had a ct scan and xray .   after 2 weeks he ran he had pain in his hips and his gate is off , The only injury he had from being hit by the car was a concussion and road rash we thought , he went from a 1650 5k runner to 21 min he tried physical therapy  and some other stuff the pain is on top of his hips  , When he runs hard his hips become out of allingn and one is higher than the other , there was blood in his pelvis when the ct scan was done.
Please help we had a mri and it shows nothing but the pain is still there.