Heel injuries can have many different causes. Pain on the bottom of the heel is very common and is often due to the strain of a ligament called the plantar fascia. This condition is often mistakenly blamed on a heel spur, which in actuality is rarely ever the cause of pain under the heel. Other injuries causing pain on the bottom of the heel can also include stress fracture or bone bruise to the heel bone, although these are less common. On the back of the heel, injury and tendonitis of the Achilles tendon can cause pain. In this case, a spur on the back of the heel bone can actually be a potential source of pain and a source of chronic injury to the tendon.