One hundred and nine patients with pronated or highly pronated feet were randomized to receive either prefabricated foot orthoses (n=52) or no intervention (n=57). The primary outcome of interest was change in Foot Posture Index (FPI) over 6 months. Secondary outcomes included the proportion of patients who improved from highly pronated to pronated posture, from pronated to neutral posture, changes in individual FPI criteria, and the influence of foot morphology on treatment outcomes. Outcomes were assessed at baseline and after 6 months. Overall, the results of the study revealed that the use of prefabricated orthoses significantly improved foot posture (p = 0.001), with greater improvements in those with highly pronated feet. However, this effect was mitigated in individuals with the index minus metatarsal formula. These findings suggest that prefabricated orthoses can effectively reduce foot pronation in the short term and may serve as a viable initial intervention in asymptomatic patients.