Flat feet happen when the arch of the foot is low or fully collapsed so the whole sole touches (or nearly touches) the ground while standing. They can be present from childhood or develop later in life for several different reasons.

Quick Scoop: What causes flat feet?

1. You can simply be born with them

For many people, flat feet are just how their feet are built.

  • Genetics: Flat feet often run in families; some people’s arches never really form as they grow.
  • Normal in babies and toddlers: All babies start out with “flat” looking feet, and arches usually form by age 2–3, but in some children they never fully develop.
  • Congenital conditions: Some birth-related or genetic conditions can lead to flat feet, like cerebral palsy, Down syndrome, Ehlers-Danlos syndrome, Marfan syndrome, and other ligament or muscle disorders.

Think of it like eye color—some families just have naturally flatter arches, and it’s not automatically a problem.

2. Loose or tight tissues around the foot

The soft tissues that support your arch play a big role.

  • Loose ligaments (hypermobile joints): If your ligaments are naturally lax, the arch can sag and stay low.
  • Congenitally tight calf muscles or Achilles tendon: When the calf or Achilles is tight, the foot can compensate by rolling inward and “flattening” the arch.
  • General tissue stretch over time: With years of standing, walking, or repetitive strain, the supporting tissues can stretch and the arch can gradually drop.

3. “Fallen arches” that develop later in life

Some people have normal arches when they’re young but lose them as adults.

  • Posterior tibial tendon dysfunction: This tendon is one of the main supporters of the arch; if it becomes inflamed, weakened, or torn, the arch can collapse on that side (often in just one foot at first).
  • Arthritis in the foot: Both wear‑and‑tear (degenerative) and inflammatory arthritis can deform the joints in the midfoot, changing the shape of the arch.
  • Foot or ankle injury: Fractures, dislocations, or ligament damage can disrupt the “architecture” of the foot and lead to flat feet.
  • Charcot foot in diabetes: Severe nerve damage and bone weakening in people with diabetes can cause collapse of the arch.

4. Lifestyle and health factors that increase risk

Certain factors don’t always cause flat feet by themselves but make them more likely.

  • Aging: Support structures in the feet weaken with age, and arches can slowly fall.
  • Obesity or high body weight: Extra load on the feet can overstretch ligaments and tendons that support the arch.
  • Long-standing diabetes: Can affect nerves and circulation, increasing risk of tissue damage and deformity.
  • High blood pressure and other systemic conditions: Sometimes associated with changes in blood vessels and tissues that may affect the feet.

5. When are flat feet a problem (and when not)?

  • Often harmless: Many adults and children with flat feet have no pain and no functional problems at all.
  • Possible symptoms: When symptoms do occur, they can include foot, ankle, knee, hip, or even lower‑back pain, especially after long periods of standing or walking.
  • Red flags to check: New arch collapse in one foot, pain along the inside of the ankle, swelling, or sudden change in how your foot looks should be checked by a clinician.

A common story doctors hear is: “My feet were normal, but over the last few years one arch dropped and now that ankle and knee hurt after work.”

6. What you can do if you think you have flat feet

This is general info, not a diagnosis, but typical next steps include:

  1. Watch for symptoms: Note when pain starts, which activities trigger it, and what shoes you wear.
  2. Try supportive shoes or insoles: Many people feel better with firm arch support and cushioned footwear.
  1. Stretch and strengthen: Calf stretches and foot‑strengthening exercises are often recommended by clinicians and therapists.
  1. Get a professional evaluation: A podiatrist, orthopedic specialist, or physiotherapist can examine your gait, check tendon function, and decide if imaging or custom orthotics are needed.

TL;DR: Flat feet are usually caused by a mix of genetics, how your arches form in childhood, the looseness or tightness of your ligaments and tendons, and, later in life, issues like tendon damage, arthritis, injuries, aging, and extra body weight. Most cases are harmless, but new or painful flat feet deserve a medical check‑in, especially if one foot changes more than the other.

Information gathered from public forums or data available on the internet and portrayed here.