A calcaneum spur (or heel spur) is often associated with plantar fasciitis and ankylosing spondylitis. A posterior calcaneum spur may also develop on the back of the heel at the insertion of the Achilles tendon.
An inferior calcaneal spur consists of a spike of calcification, which lies superior to the plantar fascia at the insertion of the intrinsic foot musculature onto the calcaneus. Until recently, an inferior calcaneal bone spur was erroneuously thought to develop at the insertion of the plantar fascia. While heel spurs are commonly associated with plantar fasciitis, they are not caused by plantar fasciitis and many people who suffer from plantar fasciitis do not have heel spurs. Oftentimes, inferior heels spurs do not have to be removed as part of the treatment for plantar fasciitis. However, 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.