Haglund's Deformity develops on the back of the heel because of chronic pressure from shoes. Your foot shape can also contribute to the development of the pump bump. If you continue to wear the wrong shoes, and pressure keeps being exerted on the bump, the heel bone will become inflamed, painful, and grow even larger. Our feet literally take us places all day long, and foot pain is a fairly common issue. For some people, the pain is located more in the heel. That heel pain can also lead to the discovery of a bump on the back of the heel. This could be a condition known as a Haglund’s deformity. 11/07/2018 · Haglund's deformity is a bony bump that appears on the back of the heel bone. This bump forms where the Achilles tendon attaches to the heel. The condition often needs treatment if it causes pain or walking problems. Treatments for Haglund's deformity may initially include shoe modifications and.