I agree with Michael. I tore my hip labrum a few years ago due to a structural abnormality but many athletes tear it performing their sport. It can only be seen with an MRI, not with an xray, but an orthopedic hip surgeon can usually tell without the MRI. Any workout or exercise that causes your client to feel pain in the area is probably not helping it and could be making it worse. This injury takes time to heal from. Bad tears may require surgery.
I would definitely work closely with his Physical Therapist or orthopedist. I agree swimming could be a good alternative. In my case, I was able to teach all my Spinning classes with no problem – only jogging aggravated it.