Pes planus and posterior tibial tendon dysfunction are among the most biomechanically consequential foot conditions — and the most responsive to custom orthotic intervention.
The medial longitudinal arch is not a rigid structure but a dynamic system maintained by the interplay of bony architecture, plantar ligaments (especially the spring ligament), the plantar fascia, and the muscles of the foot and lower leg — chief among them the tibialis posterior muscle. When this system is overwhelmed, the arch collapses, the heel everts into valgus, and the forefoot abducts — producing the classic "too many toes" sign when viewing the foot from behind. This malalignment is not confined to the foot: it alters the biomechanics of the entire lower extremity, contributing to knee, hip, and even low back pain.
Posterior tibial tendon dysfunction (PTTD) is the most important and underrecognized cause of adult-acquired flatfoot. The posterior tibial tendon — the primary dynamic stabilizer of the arch — is prone to degenerative tendinopathy as it courses around the medial malleolus, an area of relatively poor vascularity. If untreated, PTTD progresses through four stages: from tendinitis with a supple flat foot, through progressive arch collapse with ligamentous failure, to a rigid, arthritic deformity that may require complex reconstructive surgery. The key clinical insight is that stage I and II PTTD are highly amenable to conservative care — but the window closes as the deformity becomes rigid.
Dr. Santopietro has extensive experience evaluating and managing the full spectrum of flat foot pathology — from the asymptomatic flexible flat foot in a child or adult who simply needs appropriate shoe support, to the adult with early PTTD who requires a custom University of California Biomechanics Laboratory (UCBL) device or articulated ankle-foot orthosis (AFO) to prevent progression. The custom orthotic prescription is tailored to the stage of disease, the patient's activity level, and their anatomy.
Other conditions in this category that Dr. Santopietro regularly evaluates and treats.
The clinical term for the early inflammatory stage of posterior tibial tendon dysfunction (PTTD) — the same condition discussed throughout this page. When the posterior tibial tendon becomes irritated and inflamed before structural deformity has set in, targeted rehabilitation and custom orthotics are highly effective at halting progression.
A congenital fusion — bony, cartilaginous, or fibrous — between two or more tarsal bones that produces a rigid or semi-rigid flatfoot. Most commonly involves the calcaneonavicular or talocalcaneal joint. Presents with recurrent ankle sprains, peroneal spasm, and a foot that cannot be fully corrected passively. Evaluation and conservative management are appropriate before considering surgical resection.
A perineural fibrosis of the interdigital nerve, most commonly between the third and fourth metatarsal heads. Produces burning, shooting, or electric-shock pain in the forefoot and toes, often with a sensation of walking on a pebble. Biomechanical factors — particularly hypermobility and forefoot splay associated with flat feet — increase nerve compression, and metatarsal padding or orthotic support frequently reduces symptoms.
With the right orthotic prescription and a biomechanically sound treatment plan, most patients with flat feet and arch pain can return to full, pain-free activity.