The Mechanics Of Plantar Fasciitis
The best way to consider how heel pain happens is to consider the mechanics of the anatomy (biomechanics). Think about a wheelbarrow! When you lift the contents of a wheelbarrow you apply effort at the handles and rotation occurs at the wheel, (the fulcrum). The load (resistance) is held up by the body of the wheelbarrow (our lever). After we apply more effort we can tip the contents of the wheelbarrow out onto the ground.
As we lift the heel off the ground we apply effort at the back of the heel by the calf muscles via the Achilles tendon. Our toe joints to the foot (metatarsalphalangeal joints) become our wheel (fulcrum) allowing rotation. The load (resistance) is our body weight moving onto the next foot. The plantar fascia and the muscles under the foot hold the foot firmly so it becomes the rigid body of the wheelbarrow (lever). As the fascia tightens due to the toes bending upwards the foot should become stiffer. This allows us to tip our body weight onto the next foot.
If the calf muscles are tight we are forced to lift the heel too early so it’s difficult to move the weight onto the next foot which isn’t ready to receive it.
This causes more strain on the plantar fascia. If the calf muscle is weak there may be a delay in heel lift causing the body weight to travel too far forward before the foot stiffens. The foot then flattens and lengthens too much, causing increased strain in the plantar fascia. If the foot muscles are too weak then when the heel lifts off the ground the foot is too flexible. The load pushes down on the foot flattening and lengthening it. This once again increases the strain on the plantar fascia. Finally, if the plantar fascia is too stiff, such as in high arched feet, there is no give in the system to allow the foot to flatten a little and then spring back. If the fascia can’t stretch out it will pull on its attachments. As the weakest attachment point is at the heel the fascia attachment is gradually over stained.
Andrew Horwood; Musculoskeletal Podiatrist, Visiting Fellow Staffordshire University