How about specific ortho provocation tests for the hip? FABER test? Gensalen's test? Scouring test? If these are positive for reproduction of groin pain, could be labral, or some OA-related pain. I'd recommend gentle hip mobs, such as long-axis distraction, and anterior-posterior glides.

Have you tested repeated movements ofthe lumbar spine?

With no symptoms distal to the knee, and a relatively recent onset of LBP, he would likely respond to lumbar manipulation.