- Flat feet is a foot type where the inside arch is low or absent, causing the foot to roll inward when standing.
- Many people with flat feet are completely asymptomatic and need no treatment.
- When flat feet cause pain — arch ache, heel pain, knee or back issues — orthotics, PT, and supportive shoes are highly effective.
- Adult-acquired flatfoot from a failing posterior tibial tendon is a different problem and requires earlier, more aggressive treatment.
- Surgical reconstruction is reserved for severe symptomatic flatfoot deformities that fail conservative care.
What are flat feet?
Flat feet — clinically known as pes planus or fallen arches — refers to a foot type in which the inside arch is low or absent. When the patient stands, the entire sole of the foot makes contact with the ground, and the foot may roll inward (overpronate). Some children are born with flexible flat feet that may or may not develop a higher arch as they grow. Adults can have flexible flatfoot that has been their normal lifelong foot type, or they can develop adult-acquired flatfoot deformity (AAFD) when a key tendon supporting the arch — the posterior tibial tendon — begins to fail.
Many people with flat feet have no symptoms whatsoever and need no treatment beyond awareness. When flat feet do cause problems, it's typically arch fatigue, inner heel pain, plantar fasciitis, posterior tibial tendonitis, or referred pain in the knee, hip, or low back from altered alignment. Adult-acquired flatfoot tends to present differently — gradual collapse of the arch over months to years, often with pain along the inner ankle.
At Northwest Extremity Specialists, our approach to flat feet starts with deciding whether treatment is even needed — which depends on whether symptoms are present and whether the deformity is progressive. Conservative care with custom orthotics, supportive footwear, and targeted PT works very well for the majority of symptomatic flat feet. Surgical reconstruction is reserved for severe progressive deformity or cases where the posterior tibial tendon has failed beyond what orthotics can support.
See it in motion
Animations licensed from ViewMedica · Swarm Interactive
The arch of the foot is supported by a combination of bones (the medial column of the foot), ligaments (especially the spring ligament), and muscles and tendons — most importantly the posterior tibial tendon, which runs behind the inner ankle bone and inserts into the arch. The posterior tibial tendon is the primary dynamic stabilizer of the arch during walking and running. When this tendon weakens, stretches, or tears — which can happen gradually with age and use — the arch collapses and adult-acquired flatfoot develops.
What it feels like
Symptomatic flat feet can present in several different ways:
- Aching, tired feet at the end of the day, especially the arches
- Pain along the inside of the foot or the inner ankle
- Heel pain, often plantar fasciitis or Achilles tendonitis
- Pain that worsens with prolonged standing or walking
- Visible collapse of the arch and inward rolling of the heel
- Difficulty rising up onto the toes (especially with posterior tibial tendon problems)
- Knee, hip, or low back pain from altered alignment in some patients
- A foot that's widening over time and harder to fit in shoes
Why it develops
Flat feet can be lifelong (often inherited) or acquired in adulthood:
- Inherited foot structure — the most common reason for lifelong flexible flat feet
- Loose ligaments (hypermobility) that allow the arch to collapse
- Posterior tibial tendon dysfunction — the most common cause of adult-acquired flatfoot
- Prior foot or ankle injury that altered structure
- Inflammatory conditions like rheumatoid arthritis
- Diabetes-related Charcot foot in advanced cases
- Obesity, which loads the arch beyond what supporting structures can handle
How we diagnose flat feet
A flatfoot exam includes a standing inspection (looking at the arch from behind and in front), a single-leg heel rise test (looking for posterior tibial tendon function), and palpation of the painful structures. Weight-bearing X-rays are taken in our office to evaluate the bony alignment of the arch, particularly important if surgical reconstruction is being considered. MRI may be used to evaluate the posterior tibial tendon if dysfunction is suspected. Most patients leave the same day with a clear diagnosis and a tailored plan.
Non-surgical care
Conservative care is the first line for almost every symptomatic flatfoot. Our typical stepped plan:
- Supportive athletic shoes with good arch support and motion control
- Custom orthotics fit to the specific foot type and pain pattern
- Targeted physical therapy for posterior tibial tendon strengthening
- Calf stretching to reduce load on the arch
- Activity modification during acute pain flares
- A walking boot or ankle brace for posterior tibial tendon flares
- Weight management when relevant
- Anti-inflammatory medication for acute pain
Surgical care
Surgical reconstruction is considered when conservative care has not provided adequate relief, when the deformity is progressing, or when the posterior tibial tendon has failed significantly. The exact procedure is tailored to the stage and pattern of the flatfoot.
- Tendon transfer (FDL to navicular) to replace failed posterior tibial tendon function
- Calcaneal osteotomy — surgical repositioning of the heel bone to restore alignment
- Lateral column lengthening osteotomy
- Cotton osteotomy or arthrodesis for additional arch support
- Triple arthrodesis (fusion of three hindfoot joints) for severe rigid deformity
Flatfoot reconstruction is one of the longer recoveries in foot and ankle surgery. Patients are typically non-weight-bearing for 6–8 weeks, then transition through a boot for another 4–6 weeks, then athletic shoes by 3–4 months. Full return to sport and high-impact activity is typically 6–12 months, with significant improvement continuing for a year or more.
When to see a specialist
- New or worsening arch or inner-ankle pain — could be posterior tibial tendon dysfunction, which benefits from early treatment
- A visibly collapsing arch over months or years
- Difficulty rising onto the toes
- Foot fatigue or pain that's changing how you walk or stand
- Knee, hip, or back pain that you suspect is related to your feet
Flat feet are evaluated by any of our board-certified podiatrists. Posterior tibial tendon dysfunction and adult-acquired flatfoot are often managed by Dr. Mia Horvath, Dr. Thomas Melillo, or our orthopedic specialist Dr. Ron Bowman. Surgical reconstruction is performed at our Tigard Locust office.