Sounds like what is now becoming evident is the overactive lateral hamstring with resultant posterior lateral knee joint compression. Remember that area is tender to palpate in a normal subject. It all sound familiar to my body when my quads were to weak! My suggestion of increased seat height for a few rides, and then lowering for a few rides is no joke, it does let the body feel where the weak areas are and you can almost feel their weakness leading to the resultant change in recruitment and maybe even pain/discomfort. Even moving the seat back an inch will put pressure back to the quads and tell him not to pull up to much on that leg by "scrappinh the heal" at the bottom of the crank. He might be over doping this with a weak psoas.

Unfortunately if he is an amateur athlete then this willall result in a reduction in road speed initially. But only initially. Amateurs are the most difficult to treat but you have to convince them on this. If he gets the mechanics right the body will heal itself.

Thanks for the update. It's great to hear back on how things are progressing. 8o