Flat Feet in Adults: What's Actually Causing Your Pain

Flat feet may have been part of your life for decades. Maybe a doctor mentioned it once, maybe you noticed it yourself. For years it wasn’t a problem. Now your feet ache after long days, your knees bother you, or your lower back feels constantly tight. You’re wondering whether your flat feet are finally catching up with you — or whether something else is going on. In reality, it’s often both.

Flat feet (pes planus) simply mean your arch makes full or near‑full contact with the ground when you stand. Adults typically fall into two types: flexible flat feet, where the arch appears when sitting or standing on your toes but collapses under load, and rigid flat feet, which remain flat regardless of position. Most adults have the flexible type. Flat feet also differ by cause: some people never developed a full arch, while others develop adult‑acquired flatfoot, often due to posterior tibial tendon dysfunction — the tendon responsible for supporting the arch.

Many people with flat feet never develop pain. Research shows a large portion of adults have low arches without any functional problems. This shifts the focus from foot shape to foot function. A flat foot that moves well and doesn’t create compensatory strain is not a problem. A flat foot that causes the ankle to roll inward, the knee to collapse, and the hip to compensate with every step is.

When flat feet do cause symptoms, the pain often appears far from the foot. Arch collapse leads to overpronation, which triggers a chain reaction: the ankle rolls inward, the shin rotates, the knee tracks poorly, and the hip and lower back absorb abnormal load. Common pain patterns include plantar fasciitis, posterior tibial tendon pain, shin splints, medial knee pain, hip tightness, and lower back strain.

Orthotics can help by supporting the arch and reducing overpronation. But they treat the symptom, not the cause. If the muscles that should support your arch are weak, an insert doesn’t fix that — it manages it.

Physical therapy focuses on restoring function rather than changing your arch shape. Treatment includes intrinsic foot strengthening, posterior tibial tendon loading, calf and ankle mobility work, hip and glute strengthening, and gait retraining. When the foot, ankle, and hip work together again, pain decreases and movement becomes efficient — even with a flat arch.

Flat feet don’t have to mean a lifetime of pain. At Wellness Rehabilitation Inc., we help adults identify the root cause of their symptoms and restore function through targeted, progressive treatment. Call 301‑493‑9257 or click here for a Free 20‑minute Discovery Call.

Cynthia Weiss, PT