Ankle Foot Orthoses (AFOs) to promote walking ability are a common treatment in patients with
neurological or muscular diseases. However, guidelines on the prescription of AFOs are currently
based on a low level of evidence regarding their efficacy. Recent studies aiming to demonstrate the
efficacy of wearing an AFO in respect to walking ability are not always conclusive. In this paper it is
argued to recognize two levels of evidence related to the ICF levels. Activity level evidence expresses
the gain in walking ability for the patient, while mechanical evidence expresses the correct functioning
of the AFO. Used in combination for the purpose of evaluating the efficacy of orthotic treatment, a
conjunct improvement at both levels reinforces the treatment algorithm that is used. Conversely,
conflicting outcomes will challenge current treatment algorithms and the supposed working
mechanism of the AFO. A treatment algorithm must use relevant information as an input, derived
from measurements with a high precision. Its result will be a specific AFO that matches the patient's
needs, specified by the mechanical characterization of the AFO footwear combination. It is concluded
that research on the efficacy of AFOs should use parameters from two levels of evidence, to prove the
efficacy of a treatment algorithm, i.e., how to prescribe a well-matched AFO.