What is plantar fasciitis (pathophysiology)?Let's begin with the structures involved. The plantar fascia is a thick fibrous band of tissue originating on the bottom surface of the heel bone (calcaneus) and it spreads out,inserting to the base of your toes. The calf muscles (gastrocnemius and soleus) attach to the back of the heel bone via the achilles tendon and can be a factor contributing to the symptoms of plantar fascitis. The calf and plantar fascia work together in the propulsion phase of gait. The calf muscles provide a contractile element of propulsion while the plantar fascia acts like a "loaded spring" as it is put on a stretch in the early phase to mid phase of propulsion.
The injury comes from excessive stress on the plantar fascia, which can be caused by multiple factors. Those factors include:
- a lack of flexibility of the plantar fascia and/or the gastrocnemius/soleus muscles
- weakness in the muscles of the foot or ankle
- increases in weight bearing forces (weight gain or increased weight bearing activities),
- poor proprioception (balance sense) or structural foot deformity
The pain that is felt is due to the pull on the periosteum (outer layer) of the heel bone, which is rich in nerve endings. Often there is a bony growth (bone spur) associated with this diagnosis if it has been present for a prolonged length of time. Remember it is the tension on the bone that produces the symptoms, not the bone spur. The bone spur forms due to the tension on the bone which causes the growth.
What are the symptoms?
- Heel pain at the origin of the plantar fascia when weight is put on the foot or when standing on tip toes. Also tenderness and swelling may occur under the heel with the possibility of numbness along the outside of the sole of the foot.
- Pain is usually worse first thing in the morning or upon rising after a long period of non-weightbearing due to what is known as "physiological creep." Physiological creep is defined as the gradual shortening of tissue over a period of time. After a few minutes of weightbearing it eases as the foot gets warmed up, but can get worse again during the day especially after walking a lot. During the night as the foot is relaxed in a plantar flexed position, the plantar fascia becomes shortened. Pain is increased on initial weight bearing due to greater tension pulling at the origin of the plantar fascia. The sheets of the bed at night could be your enemy if they press the foot into further plantarflexion (especially when lying on your back). Like any tissue kept in a shortened position, the plantar fascia will be less mobile when asked to lengthen immediately upon weight bearing. Add to this an inflammatory problem, which is allowed to settle at rest, and you will experience an even greater perception of tightness and greater aggravation on the first step out of bed.
What can YOU do?
- Get a diagnosis. While plantar fasciitis is common, there are other problems that can mimic this condition. Visit a sports doctor, podiatrist, chiropractor or physiotherapist and get a proper diagnosis.
- Treatment can include many forms of therapy, orthotic presription, night splints, cortisone injections, shockwave therapy and surgery in stubborn cases.
Kisner, Carolyn, and Lynn Allen Colby. Therapeutic Exercise, Foundations and Techniques, 4th edition. F.A. Davis Company. Philadelphia. 2002.
Prentice, William E. Arnheim, Daniel D.. Essentials of Athletic Training, 4th edition. WCB/McGraw Hill. Toronto. 1999.
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