Thanks for your replies.

I really hope it isn't a labral tear, and trying to be objective, I don't think it is one. I'm not getting what I would call 'pain' from it and it hasn't deteriorated over time. The discomfort I get is more of a niggling pull or ache.

I had a quick go at conducting a Thomas Test on myself but didn't get anything obvious. I have previously thought it might be caused by an anterior pelvic tilt (brought on by a tight psoas) but after a week or two of trying to counter that I decided it probably wasn't that.

Can anyone hypothesize why lying on my problem side, lying on my front, or sitting with my legs crossed at the ankles, might aggravate the situation? I can go to bed feeling fine, allow myself the luxury of sleeping on my left/front and within half-an-hour I can feel I've irritated the problem area.

I'm afraid I struggle to be specific about where it's affecting me. It seems to migrate subtly from day to day and occasionally I get days where I feel completely fine. Sometimes I get a pull in the area of my psoas, sometimes its aching around my sacroiliac, sometimes it feels tight in my piriformis, and sometimes my ITB along the outside of my hip feels tight. When I get the clicking it is just somewhere internal that I can not place. The pull in my knee when I open my legs outwards is on the outside of the knee, not the inside.

One other symptom I haven't mentioned yet: I can run without any problems, but I can't sprint properly. Sprinting feels mechanically impeded and it also causes quite a strong ache in the back of my left knee.