plantar fasciitis, swelling or degeneration of the plantar fascia, the thick band of connective tissue that runs across the bottom of the foot and connects the heel bone to the toes. Plantar fasciitis causes dull or stabbing pain, typically after a long period of rest, such as sleeping or sitting. The term fasciitis means “inflammation of the fascia”; however, because plantar fasciitis involves degeneration, rather than inflammation, the term fasciosis is sometimes used to describe the condition. Plantar fasciitis is estimated to account for about 11 to 15 percent of reported cases of foot pain among adults and to affect roughly 10 percent of individuals in their lifetime. It is more common in runners and persons who are overweight, particularly females.

　　Anatomy The plantar fascia originates at the heel bone and stretches across the bottom of the foot before dividing into five bands that surround the individual flexor tendons as they extend to the metatarsal heads at the toes. At the back of the foot, the plantar fascia blends with the sheath of the Achilles tendon, and in the foot, it interacts with muscles and skin. The primary function of the plantar fascia is biomechanical in nature; it provides essential dynamic support to structures through the arch of the foot and the toes. In particular, it serves as a shock-absorber during weight-bearing activities; the heel absorbs as much as 110 percent of body weight during walking, with the fat pad of the heel dissipating as much as 250 percent of body weight during running.

　　Symptoms, causes, and risk factors The most common symptoms of plantar fasciitis are stiffness and pain in the bottom of the foot, especially at or near the heel. Stiffness and pain may persist but are usually most severe after a period of rest, such as during the first several steps after getting out of bed or following exercise, particularly after intense activities such as running or jumping. Often stiffness subsides with walking. Persistent pain may be especially noticeable when climbing stairs or even when standing for a while. The area also may be painful to the touch, and pain may be further characterized by a burning sensation in the foot.

　　Plantar fasciitis is a degenerative condition, in which stress on the plantar fascia causes the tissue to lose its elasticity, which can occur over time or with overuse, overloading, or excessive stretching. Plantar fascia stress is often associated with standing for prolonged periods (such as during the workday), being overweight or obese, having very low or high arches, running or engaging in other activities that involve high impact on the feet, or wearing high heels or improperly fitting footwear. Such risk factors presumably introduce microtears in the tissue. In rare instances, plantar fasciitis is caused by other conditions, such as rheumatoid arthritis or lupus.

　　Diagnosis and treatment Plantar fasciitis is diagnosed based primarily on medical history and physical examination. Visualization by X-ray or magnetic resonance imaging (MRI) is sometimes performed to exclude the possibility of other conditions, such as a stress fracture or nerve compression in the foot.

　　Short-term treatment usually involves resting the foot and applying ice to the painful area. Topical or oral painkillers may be prescribed to reduce pain. Treatment also often involves stretching and strengthening exercises directed at the plantar fascia and other lower-leg muscles. In addition, custom orthotic footwear or supports may be used to more evenly distribute pressure on the bottom of the foot while standing or performing physical activity, and specialized splints may be worn to promote stretching of the plantar fascia and lower-leg muscles while sitting or sleeping.

　　Get a Britannica Premium subscription and gain access to exclusive content. Subscribe Now In more serious cases, steroid injections into the heel may be needed. Tissue repair or removal can be carried out using ultrasonic techniques, though severe cases may require gastrocnemius recession, a surgical procedure that lengthens the gastroc tendon (a part of the Achilles tendon) to relieve tension in the plantar fascia. Recovery from gastrocnemius recession typically takes 6–18 months. If the condition is left untreated, the plantar fascia is subjected to further irritation and degeneration over time, and chronic pain can cause affected individuals to change their gait, leading to secondary foot, knee, hip, or back problems.