Whenever an athlete presents symptoms of plantar fasciitis, medial tibia stress syndrome, PFSS etc., our first instinct is foot posting. However, it may not be a good place to start. Always look globally at what is going on with the rest of the body. Let's take achilles tendinitis as an example. Many proximal postural asymmetries can contribute. A kyphotic running posture can move the athlete's center of gravity forward as to pre load the tendon. The arms crossing the mid line of the body can create excessive long axis rotation, creating a "wringing out" effect at the tendon.
Never forget the body is a linked system. So, you have to keep in mind that an orthotic may help out the foot, but screw up the body somewhere else. Tim Sensor, head ATC at Kean University in N.J., makes these accommodating molds that are not as rigid as a traditional orthotic and usually does the trick. 1/8-1/4" felt comes in handy too.
Of course an orthotic can be a valuable modality, provided it is used in the context of the big picture.