Has anyone had a bike fit done with their bike? And did it help?

I have been road riding for quite some time and I have also been an avid mountain biker since 1999. I have never had any trouble with my leg or knee but last summer I think I over did it a bit. I pulled a muscle (inner thigh muscle) and that injured muscle caused irritation to a tendon that runs around my knee cap (to the right of my right knee cap if you were looking at me from in front of me). I went to PT and they massaged my thigh muscle while putting cortisone on my tendon with ultra sound and another device (electrical) that helped the body absorb the cortisone. It worked. The swelling in the tendon went away and the inner thigh muscle felt better. I started riding my mountain bike with no trouble at all. THEN I went on a road ride last weekend and 12 miles into my ride my thigh felt like it was pulling, it felt tight, and my knee started to hurt and burn (not the patella but the right inside of it). I called my PT and she suggested I come back for a bike fit.

So anyone have any experience with bike fitting?

Thanks guys!

Sue