Foot orthoses are commonly used in runners for treatment of overuse injuries. In spite of the number of success, the mechanisms of how foot orthoses reduce overuse pain are not well understood. Thus, the purposes of this thesis were to investigate the effects of foot orthoses on lower extremity kinematics, kinetics and muscle activity and to understand why foot orthoses reduce pain related to overuse injuries in runners.

The results showed that the custom-made foot orthoses significantly reduce pain for patellofemoral pain syndrome runners. Such foot orthoses had systematically changed internal knee rotation and EMG intensity ratio between the VMO and VL in all subjects. The amount of pain reduction was related to the amount of increase of EMG intensity for the VMO. This information suggests importance of neuromuscular effects of foot orthoses and helps to understand the mechanisms of foot orthoses in treatment of patellofemoral pain syndrome.