Haglund's Deformity (also known as "pump bump" or "retrocalcaneal bursitis") is a painful enlargement of the back of the heel bone that becomes irritated by shoes.
It normally appears as a red, painful, and swollen area in the back of the heel bone. Women tend to develop the condition more than men because of the irritation from rigid heel counters of shoes rubbing up and down on the back of the heel bone.
Changing shoes, soaking feet, and anti-inflammatory medications often mitigate the symptoms of this problem. Consult with your physician before taking any medications.