EVIDENCE-BASED ANSWER
THAT DEPENDS on whether the pes planus (flatfoot) is flexible or rigid. Flexible flatfoot (FFF)—an arch that is flat only with weight bearing—usually doesn’t require treatment at all, unless it’s symptomatic. Rigid flatfoot (RFF)—a low-lying arch that persists with and without weight bearing—may require surgery.
FFF doesn’t increase the risk of injury or pain during exercise (strength of recommendation [SOR]: B, 2 small prospective cohort studies). Treating FFF with orthotics doesn’t change the course of arch development (SOR: B, 2 small randomized controlled trials [RCTs]). FFF is usually asymptomatic, but symptomatic FFF may respond to activity modification, orthoses, and stretching (SOR: C, expert opinion).
Rigid flatfoot results from trauma, neuromuscular disorders, or congenital bone malformations (SOR: C, expert opinion). Treatment may require surgery, including osteotomy and arthrodesis, depending on the underlying pathology (SOR: C, expert opinion). No long-term outcome studies of surgical treatment have been performed.
Evidence summary
Pes planus has no universal radiographic or clinical definition, although it can be classified as rigid or flexible based on the mobility of the longitudinal arch. In the absence of an accepted definition, prevalence estimates vary widely.
An Austrian survey of 835 kindergartners ages 3 to 6 years found the prevalence of FFF to be 44%; the prevalence of pathologic flatfoot was less that 1%. Flatfoot was defined by clinical inspection and laser scanning. The study also found that prevalence decreases with age (54% at 3 years, 24% at 6 years) and that boys had a higher rate of FFF (52%) than girls (36%).1
Flexible flatfoot doesn’t affect function
Ligament laxity is thought to be the primary cause of the abnormally low-lying longitudinal arch associated with weight bearing that characterizes FFF. A small (N=230) prospective cohort study showed that the foot shape of Australian military recruits was unrelated to pain, injury, and functioning during an 8-week basic training course.2
Another prospective cohort study of 246 male US Army recruits enrolled in a rigorous 12-week infantry training program found that trainees with low or flat arches actually had a lower risk of foot injury than trainees with high arches.3
Few studies evaluate FFF conservative treatment
Conservative therapies traditionally used to treat symptomatic FFF include physical therapy, orthotics, and corrective shoes. Few studies of their efficacy exist, however. Although we found no studies of adults or adolescents with symptomatic FFF, we did find a few studies of younger children with noticeably flat feet and concerned parents or physicians who referred them for therapy.
A prospective study followed 129 children with FFF (1-6 years old, mean age 29 months) who were referred by pediatricians to Texas Scottish Rite Hospital Flatfoot Clinic, which was set up entirely for the sake of the study, based on cosmetic appearance as well as functional symptoms. The children were randomized to 1 of 4 groups—controls, corrective orthopedic shoes, heel cups, and custom-molded inserts—and followed for 3 years.
The authors, who were blinded to group assignment, measured 14 outcomes related to foot shape and function. They quantified radiographic changes, not patients’ clinical or functional outcomes. All of the outcomes showed improvement in all 4 groups; no significant differences were noted between children who received active interventions and controls. Thirty-one patients were dropped from the study because of noncompliance and weren’t included in the final analysis.4