The plantar fascia is a band of fibres that run from the heel to the base of the toes. Plantar fasciitis occurs when these fibres become irritated, partially torn, or over-stretched. Most commonly over-pronation results in a constant tugging of the plantar fascia attachment site (at the heel). Inflammation results from this constant irritation and scar tissue begins to repair the site of injury. Pain and tightness occur in the arch or heel upon weight bearing. Pain is typically worse in the morning with the first steps as the foot assumes a flexed position during sleep and the plantar fascia contracts. The pain gradually improves with activity and eases throughout the day.
A number of factors contribute to the development of plantar fasciitis including: a leg length difference, overpronation, a supinated foot, inappropriate footwear, muscle tightness, overtraining and overuse. Because the condition is caused by repetitive microtrauma, most athletes experience plantar fasciitis as part of an overuse syndrome following changes in their training regimen.