Pain in your heel is most commonly attributed to plantar fasciitis--inflammation of the plantar fascia along the bottom of the foot. This condition can be caused by repetitive stress on the feet from sports, from standing for long periods of time, or from obesity. However, there are also several other conditions that can lead to pain in the heel.
Achilles tendinitis can cause heel pain along with pain in the back of the legs. The stress on the Achilles tendon often causes it to pull on the heel where it attaches to the bone. This condition is most commonly attributed to a sudden increase of activity such as lengthening the duration of your exercise routine.
Another reason for heel pain is the presence of a heel spur. This is a bony growth of calcium located under the heel bone (also known as the calcaneus). This condition often accompanies plantar fasciitis.
If your heel pain is severe, and has lasted for an extensive period of time, it may be due to a stress fracture in the heel. Bone breaks require a great amount of rest and time to heal before normal use of the foot can resume.