A calcaneal spur (or heel spur) is a radiological finding, and when it is located on the inferior aspect of the calcaneus, is often associated with plantar fasciitis and ankylosing spondylitis. A posterior calcaneal spur may also develop on the back of the heel at the insertion of the Achilles tendon. An inferior calcaneal spur consists of a calcification of bone, which lies superior to the plantar fascia at the insertion of the plantar fascia . Posterior heel spurs are often large and palpable through the skin and may need to be removed as part of the treatment of insertional Achilles tendonitis.