Wednesday, 11 February 2015 09:40

What Causes Plantar Fasciitis?

You know plantar fasciitis (PLAN-tur fas-e-I-tis) when you have it - a sharp, searing, knife-like pain on the bottom of your heel. In the morning, that first step out of bed can be excruciating, becoming less so as you walk and warm up the muscles and the plantar fascia ligament. Pain can also make itself known when you stand up after sitting for a while.

"itis" is a medical suffix used to indicate the inflammation of an organ - in this case the plantar fascia.plantar fasciitis

To understand plantar fasciitis, a little anatomy lesson is handy. The plantar fascia is a thick ligament made of dense, fibrous tissue which has very little stretch in it. It's main function is to act as a shock absorber. The plantar fascia starts at the bottom of your heel, runs across the arch and the ball of your foot, and then spreads out, attaching at the base of the toes.

When you take a step, and as your foot impacts the ground, your foot actually flattens, which lengthens the foot ever so slightly. This causes the plantar fascia to lengthen as well, as much as it can (remember, it doesn't have much stretch in it). Then when your heel lifts off the ground, the ligament returns to normal. When your foot impacts the ground hard, such as when playing sports, the foot flattens a little more than usual, and the plantar fascia stretches a little further than it would like to. As a result, small, usually minute tears develop where the ligament attaches to the heel bone (calcaneus). These small tears cause the ligament to bleed a little, and the tension of the plantar fascia pulling at the heel bone causes a spur to form on the bottom of the heel. However, the heel spur is not the cause of pain - it's caused by the plantar fascia trying to tear away from the heel bone. Many people have heel spurs and have no pain whatsoever.

Why does your foot flatten and tear the plantar fascia? The answer lies just below your ankle.  When your foot contacts the earth, the subtalar joint, just below your ankle joint, flexes to absorb the impact. The flexing of the subtalar joint causes the arch of your foot to flatten (pronation) or heighten (supination). If the foot excessively flattens, it's said to overpronate, and the plantar fascia is constantly under strain. Over time this weakens the ligament where it attaches to the heel bone, and pain occurs. Then when you are at rest, the plantar fascia starts to mend itself. But even a full night's deep sleep isn't enough to heal the plantar fascia entirely, and when weight is applied with that first step in the morning, the fascia tears again, causing pain. It is this persistent irritation of the plantar fascia that is known as plantar fasciitis.

Another contributing factor to plantar fasciitis is a tight calf muscle. The calf muscle attaches to the foot by way of the achilles tendon behind your heel. If the calf muscle is tight it limits the movement of the ankle joint, contributing to over pronation. Calf muscles can become rigid due to exercise, but also inactivity. High heels, even boot heels can cause the calf to tighten, and in some people, it's just naturally so.

Read about how PA Foot and Ankle Associates treats the symptoms of plantar fasciitis

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