The evidence clearly shows a lack of effectiveness & I am a firm believer that adequate rehabilitation negates the need for orthotic use in most cases. This systematic review which reviewed the best evidence for causes of injury in runners suggests that orthotic use is actually a risk factor for injury.
Like all research, the conclusions may not be as straightforward as they seem. One of the main risk factors for any injury is a prior history of that injury & it is likely that those who obtained orthotics did so due to a prior injury. The most logical approach is to rehabilitate your injury (ankle, knee or low back) prior to use of artificial supports such as orthotics as the long-term consequence of such supports is unknown.
Call the Physio Clinic: Naas & Newbridge for further information on: (045) 874 682