Haglund’s deformity or a pump bump or an enlarged bit of bone at the back of the heel is a real problem in runners and is not easy to deal with. The enlarged bone rubs on the shoe causing a bursitis (called retrocalcaneal bursitis) and blisters. The bursitis can become quite swollen and painful.
The only way to make the enlarged bone go away is surgery and that involved taking off the Achilles tendon to get at the bone and then reattaching the tendon. That is a big deal, so we want to avoid that if possible. It is, however, a good option in the long term if this is an ongoing problem.
The best way to deal with a Haglund’s issue is to get pressure off the painful area. A simple heel raise maybe all that is needed in some cases as this can move the painful area away from the irritating part of the heel counter on the running shoe. Podiatry adhesive felt can be used to fashion a doughnut shaped pad around the painful area. Other padding may be able to be adhered on the inside of the heel counter of the shoe to keep the pressure of the lump. If the pressure is relieved, the swelling from the bursitis can go down.
As for the best running shoes for a Haglund issue, there probably isn’t one. Most running shoes brands use a different shaped last, so its a matter of finding one that best suits the shape of the back of your heel. That is a difficult task. A running shoe with a soft, flexible and pliable heel counter is going to be better than one with a more rigid heel counter.
Some runners experiment with a higher drop and a lower drop running shoe and find that one more than another does a better job at relieving pressure on the bump. As each individual Haglund’s lump is different its hard to give specific advice to an individual as to which running shoe will suit them better.
Some runners even resort to cutting a hole in the counter of the running shoe so that there is no pressure on the bump. If you want to do that, try it first on an older pair of running shoes.