The foot is a very complicated area, that is comprised of 28 bones and many joints. These bones and joints have to move as demands on the foot change. An intricate system of muscles and ligaments controls the position of the foot and stabilizes the joints of the foot and ankle. Many of these muscles are located on the back of the calf and are attached to long tendons that cross the ankle and foot and affect the foot and toes.
Another group of muscles is located on the bottom of the foot. The vast majority of these muscles are attached to the bottom of the heel.
Located just under the skin and over the top of the foot muscles is the plantar fascia, which is very tough and dense connective tissue that runs from the bottom of the heel all the way to the toes. The fascia works to support the arch of the foot and helps to stabilize the joints of the foot when bearing weight.
Beneath the plantar fascia, muscles are arranged in layers, and each muscle in each layer has a different function. For example, some of the muscles attach all the way to the toes and act to flex and stabilize the toes, while other muscles attach to other bones of the mid-foot to control and stabilize the arch of the foot. For the foot and ankle to work properly, and to prevent pain and injury, the foot and calf muscles must have adequate strength and flexibility, the different layers of muscles need to be able to glide freely over another during normal use.
Throughout the day we use our feet a great deal. As we stand, walk, or run, a tremendous amount of pressure is placed on the foot. This creates tension on the plantar fascia, causing the muscles of the foot to contract to support the arch and stabilize the joints of the foot. Over time, the muscles of the fascia can become strained and fatigued and develop small amounts of injury, called micro-trauma. Simply stated, micro-trauma is very small-scale damage that occurs in the muscles, fascia, and ligaments in response to small levels of strain. Initially this micro-trauma is not painful, but may be perceived as a mild ache or tightness in the muscles, or at the heel where these muscles attach. Although small, this damage needs to be repaired. The body responds to soft-tissue injury (including micro-trauma) by laying down small amounts of scar tissue to repair the injured tissue. Over time, this scar tissue builds up and accumulates into adhesions. As these adhesions form, they affect the normal health and function of the muscles. In fact, adhesions often lead to pain, tightness, lack of flexibility, muscle weakness, compromised muscle endurance, restricted joint motion, altered biomechanics, and diminished blood flow.
As the muscles and fascia of the foot become strained and then develop adhesions, they become very tight. As the tightness increases, the tissue begins to pull away from the heel where it attaches, eventually leading to pain and irritation at the bottom of the heel. Sometimes with long-term muscle tightness, this constant tension can lead to the formation of a heel spur. Evidence of a heel spur on an x-ray can lead to misdiagnosing the heel spur as the cause of the pain. The problem is that the heel spur is very rarely the cause of pain, leading to inappropriate treatment.
In addition to causing pain and tightness, adhesions are very sticky, affecting the ability of the muscles to stretch, contract, and slide over one another. Every muscle in the foot has a different function, and contracts at different times, so the muscles need to be able to glide freely on one another. Adhesions cause the individual muscles layers to stick on each other, preventing the normal gliding. When the muscles lose the ability to slide and glide over one another, the entire area binds together. Think of these adhesions like the rust and grime that can build up in an automobile. Normally the parts of the car should be well oiled and move smoothly, but when rust and grime are allowed to build up, the car begins to break down until eventually it does not work properly and repairs are needed. The same thing happens in the body. Stretching or contraction of one muscle causes pull and tension on all the other muscles. This in turn causes more and more strain on the muscles and increased tension at the heel.
Another common development is that the accumulation of scar-tissue adhesions can affect the nerves in the ankle and foot. This occurs because between the layers of muscles are nerves that run from the knee down the lower leg, around the ankle, and into the bottom of the foot. Just as the muscles need to be able to glide on each other, nerves also need to be able to glide freely between the layers of muscles. In many cases the accumulation of scar tissue can cause the nerves to become stuck to the surrounding muscles and fascia. Instead of the nerve gilding easily between the muscles, it becomes stretched and irritated, leading to foot and heel pain. It is quite common for nerve entrapment at the foot or ankle to cause foot and heel pain and lead to an incorrect diagnosis of Plantar Fasciitis. Obviously, an incorrect diagnosis leads to incorrect treatment, which will not be effective in relieving the condition.