Overview
Flatfoot, also called pes planus, is a condition where the arch of the foot is low or collapses, changing how the foot contacts the ground. The problem can be flexible, where the arch may appear when you are not bearing weight, or rigid, where the arch stays low in most positions. Over time, abnormal foot mechanics can overload structures like the posterior tibial tendon and the joints, which may lead to pain, stiffness, and reduced walking comfort. Some people are born with flat feet, while others develop flatfoot later due to tendon wear or injury.
Symptoms
People with flatfoot often notice pain along the inner ankle/arch, aching after standing, and difficulty staying on their feet for long periods. Shoes may wear down more quickly on the inside edge, and the foot may look wider or flatter than before. Symptoms often worsen with walking, running, hills, or prolonged standing, especially if the arch collapses under load. In some cases, the condition can contribute to heel pain or foot fatigue and make balance and push-off weaker.
Causes
Flatfoot can be congenital, meaning the arch is low from childhood and may be flexible. Adult-acquired flatfoot commonly develops when supporting structures, especially the posterior tibial tendon, become strained or degenerates and can no longer support the arch. Injury, arthritis, nerve problems, or obesity can also contribute by changing alignment, loading patterns, or tendon function.
Risk Factors
Flatfoot is more likely if you have a family history of low arches or if you developed flexible flat feet during childhood. In adults, risk increases with age-related tendon wear, prior foot or ankle injuries, and conditions that affect connective tissue or muscle function. Being overweight, having diabetes, and working in jobs with long periods of standing can also increase the likelihood of symptoms and progression.
Prevention
You can reduce flare-ups by using supportive footwear and avoiding abrupt increases in walking, running, or weight-bearing activity. Strengthening the foot and ankle (especially supporting muscles and the posterior tibial tendon pathway) and daily calf/arch stretching can improve tolerance to activity. Maintaining a healthy weight and taking breaks during long standing can lower repetitive overload on the arch.
How the Diagnosis Is Evaluated
Clinicians usually start with a history of pain location, onset (childhood versus adulthood), and whether the arch changes between non-weight-bearing and standing. A physical exam checks foot alignment, range of motion, flexibility versus rigidity, tenderness, and whether you can perform single-leg heel rise, which may suggest tendon involvement. Imaging is not always required, but X-rays can help assess alignment and arthritis, and ultrasound or MRI may be used if tendon tear, inflammation, or another cause is suspected.
Nonsurgical Treatment Options
Treatment focuses on reducing pain and improving arch support and mechanics. Supportive shoes, custom or over-the-counter orthotics, and medial arch support help offload the plantar and tendon structures and can improve comfort during daily walking. Physical therapy commonly includes strengthening (foot intrinsic muscles and ankle invertors), stretching of the calf/plantar tissues, gait training, and activity modification to avoid overload. Anti-inflammatory medications like NSAIDs can help short-term pain control when appropriate. If symptoms flare despite conservative care, a short period of immobilization in a boot and/or a corticosteroid injection may be considered for targeted pain relief. Some patients with persistent tendon-related pain may ask about biologic injections such as PRP, but results vary and these are typically considered after standard therapy has been tried.
When to Seek Medical Attention
Seek medical attention if you have new or worsening pain that limits walking, especially pain concentrated in the inner ankle/arch. Get prompt evaluation if you cannot bear weight, if there is sudden worsening after an injury, or if you notice major swelling, redness, or fever. You should also seek care urgently if you develop numbness, progressive weakness, or other neurological symptoms, or if you notice rapidly changing foot position.
Frequently Asked Questions
Flatfoot can be congenital or caused by tendon strain and wear, arthritis, injury, or conditions that change foot mechanics.
If your arch looks higher when you are not bearing weight but flattens when you stand, it is often flexible; a clinician can confirm this on exam.
Next Steps
If your flatfoot is causing pain, start with an evaluation by a clinician who can assess whether it is flexible versus rigid and whether a tendon or joint issue is contributing. In the meantime, use supportive footwear and consider an arch-support insert to reduce strain while you arrange care. If symptoms are worsening or you have trouble bearing weight, seek evaluation sooner rather than later.