Experienced runners get different injuries than beginners. Beginners are famous for shin splints and runner's knee. Long-time runners work for their injuries. The most common injuries seen in experienced runners are muscle knots or "trigger points". These injuries start as very minor micro-tears. Next, a repetitive tear-and-repair cycle causes a know or a trigger point to develop. The runner then starts to experience pain and stiffness in the area. Common trouble spots include: the front and back of the thighs, the deep hip region, and the outside of the thigh, known as the IT Band.
The (almost) Magical Foam Roller | Running Times Magazine