Foot orthotics have been proven to help with the treatment of running-related musculoskeletal injuries. 70 to 80% of people with chronic knee injuries get substantial benefits from such items.
While several studies have shown a good amount of help with pain control, we do not really understand why the orthotics help so much. The mechanism remains unclear. The biomechanical changes are relatively small, and help to control rearfoot eversion, but only to a small degree. It has been hypothesized that they help to reduce the strain on our plantar fascia or help to reduce the midfoot kinematics - remember that most people show hypermobility there.
Some studies also concluded that there are no significant benefits of heat-molded orthotics compared to the non-molded ones.
As for the shoe itself, you have to consider your foot type and the mechanics associated when choosing an orthotic. You may first test an affordable, over-the-counter model to see if it brings you measurable benefits. Then decide to go for the tailor-made option to get the most of this approach.
At Hong Kong Sports Clinic, we do believe that such devices are better used temporary, to help controlling symptoms - reducing pain. We focus more on finding what could actively help with foot mechanics - joint mobility, muscle strength, etc.
Stay tuned as we move up the kinematic chain and discuss knee mechanics next!