What Is Plantar Fasciitis?

Runners and athletes with plantar fasciitis may notice heel pain that gets progressively worse during a workout. Left untreated over weeks or months, the pain may become worse or more frequent, interrupting daily activities.

See Common Running Injuries: Pain in the Ankle or Back of the Heel

Plantar fasciitis is the third most common injury for runners and sends approximately 1 million people—runners and non-runners alike—to U.S. doctors each year.1,1

See Common Running Injuries

Understanding the condition, its symptoms, and how to treat it, can help plantar fasciitis sufferers alleviate pain and get back into their routines.


What Is the Plantar Fascia?

“Plantar” refers to the bottom of the foot and “fascia” refers to fibrous connective tissue, so the plantar fascia is a fibrous band of tissue on the bottom of the foot. It begins at the heel bone (calcaneous) and widens as it spreads out and attaches to the long bones—called the metatarsals—at the ball of the foot.

The plantar fascia helps to maintain the arch of the foot and plays an important role in foot stability and movement. As the foot moves so does the plantar fascia:

  • When the un-weighted foot is at rest, the ankle joint is in neutral and the plantar fascia is shortened.
  • When standing and the foot weighted, the plantar fascia is lengthened.
  • When walking or running, the foot strikes the ground and the arch of the foot flattens, stretching out the plantar fascia. It then rebounds, helping the foot push off the ground.

If the plantar fascia ruptures the arch of the foot will collapse, resulting in flat feet.

How Does the Plantar Fascia Cause Pain?

When walking or running, each stride causes the plantar fascia to stretch and contract. Just walking or running a few miles causes the plantar fascia to stretch and contract thousands of times.

This repeated stretching and contracting can cause:

  • Tiny tears, called micro-tears, to develop in the plantar fascia
  • Inflammation of the plantar fascia

Inflammation and/or micro-tearing typically occur near where the plantar fascia attaches to the heel bone, which is why pain is felt in the heel.


The inflammation and micro-tearing may happen individually or together; chronic inflammation makes the fascia weaker and prone to tearing, and micro-tearing makes the fascia prone to inflammation. If micro-tearing occurs without inflammation it is technically considered plantar fasciosis, but most people still refer to it as plantar fasciitis.

Pain after resting
People with plantar fasciitis often feel heel pain when getting out of bed. As a person sleeps, the ankles rest at 100- or 110-degree angles, allowing the plantar fascia to relax and shorten. Once the person stands, the ankles are at 90-degree angles and the plantar fasciae are weighted and forced to stretch, which can cause pain.

See Is Heel Pain Caused by Heel Spurs or Plantar Fasciitis?


  • 1.Taunton JE, Ryan MB, Clement DB, Mckenzie DC, Lloyd-smith DR, Zumbo BD. A retrospective case-control analysis of 2002 running injuries. Br J Sports Med. 2002;36(2):95-101.
  • 2.Riddle DL, Schappert SM. Volume of ambulatory care visits and patterns of care for patients diagnosed with plantar fasciitis: a national study of medical doctors. Foot Ankle Int. 2004;25(5):303-10.