Bursitis, that's my non-medical voice of experience opinion.
Trochanteric Bursitis to be exact if it's on the outside of the hip.
Been there done that.. MEAN pain for sure from the entire hip outside and roaring down the theigh.

Bursa are small sacs of something.. that are between the bone and muscle allowing easy sliding of the muscle over the bone. When the bursa get smashed they tend to scream at you.

Mine was caused by my spine bending and pulling the muscles too tight over and therefor smashing and irritating the bursa on my hips Greater Trochanteric bone.

To get the diagnosis..
I Had the hip Xrays that showed no new problems, no hip arthritis.
I Had an MRI upon which they said Trochanteric Bursitis on the report

Got the steroid shot (wonderful relief after 3 days)

But of course my spine continued to bend so the bursitis was unhappily reoccurring.

Did PT, helped only a tiny bit.

Found a Chiropractor to help subjegate the bending of my spine....
GREAT results after many visits (It's not a short term commitment) and the hip bursitis pain monster is currently NICELY controlled.

To NOT have that constant monster pain any more is so wonderful.

I will continue seeing my Chiro since my spine will continuely need subjegated as it continues attempting to bend convexly to the left. The bending spine is due to my osteoarthritis and osteoporisis.

I hope you solve your problem.

Please forgive my bad spelling and lousy typing!