Foot drop is the second most common functional deficit affecting human locomotion that an orthotist will encounter. Foot drop is a symptom. Its overall incidence has not been reported due to the variety of injuries and conditions that cause it. Although it appears that individuals with foot drop have a simple deficit with a simple solution, for the majority of patients, foot drop is a complicated issue and is often accompanied by severe long-term physical ramifications. Nearly all people with untreated foot drop will develop significant secondary and progressively worsening deformities over time, as will those who are fitted with orthoses to treat the functional foot drop alone.