What is plantar fasciitis? The plantar fascia is a thick band of connective tissue that runs from the heel bone to the base of the toes and supports the foot arch. Plantar fasciitis is a common overuse injury that causes swelling of the plantar fascia at its attachment site on the heel bone. Inflammation can occur primarily at the point where the tendon connects to the heel. Repetitive stretching or tearing, which can cause irritation and inflammation, is one of the most common causes. The heel is a part of the body designed to absorb impact when you bear weight. If pain develops, it can be extremely debilitating, making even standing or walking difficult.