Each time we take a step forward, all of our body weight first rests on the heel of one foot. As our weight moves forward, the entire foot begins to bear the body's weight, and the foot flattens and this places a great deal of pressure and strain on the plantar fascia. There is very little "give" to the plantar fascia, so as it stretches only slightly, it pulls on its attachment to the heel. If the foot is properly aligned this pull causes no problems.
CAUSES:
Common causes of pain in the bottom of the heel, the arch, or both the heel and the arch, are heel spurs and plantar fasciitis.
During resting or non-weight bearing periods, the plantar fascia shortens. When body weight is rapidly applied to the foot the fascia must stretch and quickly lengthen, causing micro-tears in the fascia.
Hypermobility, (excessive internal motion) of the foot can induce future or coexisting problems involving the knee, hip, sacroiliac joint or the low back region.
The most common cause is abnormal or excessive internal motion of the foot.
Supinated feet (the rolling inward of the foot, causing a break down of the outer side of the shoe) are relatively inflexible, usually have a high arch, and a short or tight plantar fascia. Thus as weight is transferred from the heel to the remainder of the foot, the tight plantar fascia hardly stretches at all, and pulls with great force on its attachment to the heel.
In both cases, the abnormal stress placed on the attachment of the plantar fascia to the heel usually causes pain, inflammation, and possibly swelling. If this process continues, the plantar fascia partially tears away from the heel. The body will fill in this torn area with calcium; eventually it becomes bone, and a heel spur results.