The ITB is a common source of irritation in both athletic individuals (such as runner s& cyclists) and the not so athletic!
Typical symptoms include a deep tooth-ache like pain on the outside of the thigh. This will often wake you up during sleep and force you to turn over. Knee pain can also be a feature, as well as discomfort or tightness in the buttocks.
I view this complaint as due to overloading of the ITB, for example from continuous contraction, overuse or sudden increases in physical exertion involving the muscles that influence the tightness of the ITB. One example of this is tramping, where days of walking with a heavy load can overload the muscles (such as the gluts), resulting in tightness. And since these help keep the ITB tensioned, that tightness gets passed on down the ITB.
Elderly patients might get the same issue without being athletic because with declining muscle strength and elasticity, it's easier to accomplish the same overloading with more mundane, everyday activities.
Whilst there are more severe cases of damage to the ITB, most cases I have seen symptoms subside quickly with treatment, which nearly always includes a lot of soft tissue work to release the muscles tensioning the area, as well as working on the ITB itself.
Other possible explanations for outer thigh pain
These would include nerve irritation from the lumbar spine and Meralgia Parasthetica, an obscure name for compression of the femoral nerve, often by soft tissues in the groin area. This also produces symptoms in the outer thigh. Hip problems are another potential cause.