A neighbor notices it at the pool. A shoe salesperson points it out. Or maybe you glanced at your own wet footprints on a Greenbelt bathroom floor and realized your arch leaves almost no gap. Flat feet are common — but does that mean you need to do something about them?
The short answer: not necessarily. Research suggests that roughly one in five adults has low or absent arches, and many of those people are completely pain-free and active for their entire lives. But for some adults, flat feet — or arches that have slowly collapsed over time — become a genuine source of pain, fatigue, and movement limitations. Here is how to tell the difference and what your options are when flat feet do cause problems.
The arch of the foot is formed by a combination of bones, tendons, and ligaments that work together to distribute your body weight with each step. When that structure collapses, the inner edge of the foot touches or nearly touches the ground — that's a flat foot.
There are two very different situations that can produce flat feet in adults:
One of the first things I assess in the exam room is whether a patient has flexible or rigid flat feet. The distinction shapes everything that follows.
| Type | What you'll notice | Common cause | Typical treatment need |
|---|---|---|---|
| Flexible flat foot | Arch appears on tiptoe or when sitting; collapses under full weight | Congenital, ligament laxity, mild PTTD | Often none; orthotics if symptomatic |
| Rigid flat foot | Little or no arch even when seated or on tiptoes; foot feels stiff | Advanced PTTD, arthritis, tarsal coalition | Evaluation always recommended; bracing or surgery may be needed |
If you can create an arch by standing on your toes, your flat foot is most likely flexible — a reassuring sign that the supporting structures are still intact and working. Rigid flat feet, where the foot stays flat regardless of position, warrant a closer look.
The most common culprit in adult-acquired flatfoot is posterior tibial tendonitis (also called posterior tibial tendon dysfunction, or PTTD). The posterior tibial tendon runs along the inside of the ankle and acts as the primary cable that holds the arch up. When it becomes inflamed, overstretched, or tears, the arch gradually collapses.
Several factors can accelerate PTTD:
Our valley draws a lot of active adults — hikers on the Foothills trails, cyclists on the Greenbelt, people who spend summers gardening or chasing kids at Roaring Springs. That's wonderful, but sustained activity on hard surfaces without adequate arch support can quietly stress the posterior tibial tendon over many years. If your feet have always felt fine and now they're starting to ache after activity, that's worth paying attention to early — before a gradual collapse becomes a bigger structural problem.
No — and this is where the conversation often surprises patients. Studies estimate that somewhere between 20 and 26 percent of adults have flat feet, yet a large proportion of those people have no pain at all. The foot is remarkably adaptable, and many people compensate without realizing it.
That said, flat feet can produce a recognizable cluster of symptoms when they do become a problem:
If you're noticing any of these patterns — even mildly — it's worth an evaluation rather than waiting for the pain to worsen.
Flat feet rarely exist in isolation. When the arch collapses, it changes the alignment of the entire lower limb, which can stress structures well beyond the foot itself. Common related conditions include:
The good news: the overwhelming majority of adults with symptomatic flat feet can be managed effectively without surgery. Conservative care is the starting point for almost everyone.
Custom orthotics are the workhorse of flat-foot management. Unlike the mass-produced insoles you find at a pharmacy, custom orthotics are cast or scanned from your foot and built to correct your specific arch position and gait pattern. For patients with PTTD, a medial arch support orthotic can dramatically reduce tendon load and slow or halt arch collapse. Research published in peer-reviewed literature has found that conservative treatment including bracing and orthotics achieved successful outcomes in the majority of patients treated without surgery.
Supportive footwear — shoes with firm heel counters, motion control, and built-in arch support — amplifies the benefit of orthotics. Sandals, flip-flops, and minimalist shoes tend to be the worst choices for someone with a flat, pronating foot.
The posterior tibial tendon and the intrinsic muscles of the foot can be meaningfully strengthened with targeted exercises. A physical therapist can guide you through a program that typically includes calf raises, towel scrunches, arch doming, and balance work. Consistent follow-through with home exercises, combined with orthotics, is often the most effective conservative combination.
Reducing high-impact activity during a painful flare gives the posterior tibial tendon a chance to recover. Swimming and cycling are excellent low-impact alternatives that keep you conditioned without pounding the arch. For patients with obesity, even a modest reduction in body weight can meaningfully reduce tendon stress.
Schedule an appointment if your arch ache has persisted for more than a few weeks, if pain is limiting your daily activities or hobbies, or if you've noticed your foot slowly changing shape. Seek same-day or urgent care if the inside of your ankle suddenly becomes red, hot, and severely swollen after activity or a stumble — this can signal an acute tendon rupture that needs prompt evaluation. Also see a clinician promptly if you have diabetes or poor circulation and develop any new foot pain, as delayed treatment carries greater risk of complications.
Surgery is considered when conservative care — orthotics, physical therapy, activity modification — has been pursued consistently for several months without adequate relief, or when PTTD has advanced to the point where the deformity is rigid and the joint surfaces are significantly damaged. Surgical options range from tendon repair and reinforcement to bone realignment procedures (osteotomies) or, in severe cases involving arthritis, joint fusion. Most patients, especially those who seek care before the deformity becomes rigid, never reach the surgical threshold.
The earlier the condition is identified and treated conservatively, the better the odds of avoiding a more complex intervention.
No. Many adults with flat feet are completely pain-free and active throughout their lives. Treatment is recommended when flat feet produce symptoms — arch or heel pain, ankle fatigue, shin soreness, or difficulty with activities — rather than based on appearance alone.
With flexible flat feet, a visible arch appears when you stand on tiptoe or sit; the arch only collapses under full body weight. Rigid flat feet show little or no arch in any position. Rigid flat feet are stiffer, more often painful, and more likely to require medical attention.
Yes, they can. Flat feet cause over-pronation — an inward rolling of the foot — that alters the alignment of the entire lower limb. Over time, this can contribute to knee pain, hip discomfort, and even lower back strain. Addressing foot mechanics can sometimes improve symptoms higher up the chain.
Yes. Treasure Valley Foot & Ankle is located in Meridian and sees patients from across the Boise and Treasure Valley area. You can request an appointment online or call (208) 272-9253.
Having flat feet is not a diagnosis that automatically requires treatment — it is a structural variation that matters clinically only when it starts causing symptoms. If your feet are comfortable and you're moving without limitations, there is often nothing you need to do. But if you're feeling persistent arch ache, heel pain, or ankle fatigue — or if your arches have slowly changed shape over the years — that is exactly the kind of problem a podiatrist is trained to evaluate and address conservatively, well before surgery ever enters the picture.
Dr. Clark Johnson is a board-certified foot and ankle surgeon at Treasure Valley Foot & Ankle in Meridian. If you're dealing with arch or heel pain and suspect flat feet may be contributing, request an appointment or call (208) 272-9253.
This article is for general educational purposes and is not a substitute for professional medical evaluation or treatment. If you have diabetes, poor circulation, or any sudden change in foot appearance or severe pain, please be evaluated promptly by a qualified clinician.
Get a thorough evaluation and an honest plan — from conservative orthotics to advanced care when you need it.