Dynamics of the Foot and Treatment of Foot Related Disorders
Dynamics of the Foot and Treatment of Foot Related Disorders
The foot is a functional unit made up of bone, muscle, tendons, nerves and membrane. The structure of the foot has changed very little since prehistoric times. In fact, the development of man’s brain occurred after the development of the foot. Anthropologists believe it was man’s ability to become bipedal (walk on two feet) that allowed the cerebral cortex to develop.
The foot is a complex structure.
Nearly ¼ of all the bones in the body are in the feet (52 of them). Additionally, there is a high concentration of nerve endings in the feet, like the hands. The unique structure of the foot allows it to support the full weight of the human body. It absorbs the shock of foot strike in running and is rigid enough to “toe off” at the end of the gait cycle. It does not function alone, but works in conjunction with the ankle, knee, hip and lower back.
The three phases of gait (walking).
- Heel strike: also known as proprioception or “finding the ground”. The foot is in a position of Supination (locked and rigid condition).
- Mid Stance: from heel strike to toe off. This is the shock absorbing phase where the foot becomes unlocked and the knee travels over the foot. The foot goes into a position of Pronation (unlocked and flexible).
- Toe-off: weight transferred to the ball of the foot. This allows the body to propel itself over the toes. The foot re-Supinates (locks up and becomes rigid) to provide a lever for forward momentum.
Where the problems with foot function arise.
For the foot to function properly it must be able to be locked (supinated) and unlocked (pronated) at the required phases of gait. Most foot function problems arise during Mid- Stance. If the foot over pronates it can cause stress on the plantar fascia (plantar fasciitis or heel spurs), shin splints and associated knee pain as a result of excessive tibial torsions. For those who feet are excessively rigid and do not pronate enough (supinators) the problems are typically inversion sprains, stress fractures of the small bones in the feet, knee problems associated with unnatural gait and shock to the lower kinetic chain (ankle, knee, hip, lower back). Many foot related problems occur from “over use syndrome”. “Over use” implies an injury that develops gradually as a result of a change in intensity of activity. For a runner this may be increasing mileage or speed. For many, it may be starting a new exercise program or perhaps sudden weight gain like a pregnancy.
Often, an asymmetric (one side or the other) foot, knee or back problem may be a result of a leg length discrepancy. This is very common among the population and is rarely identified during routine examinations. Leg length discrepancies of 3/8” to 5/8” are easily treated with a heel lift (correcting to ½ the discrepancy). More extreme cases may require shoe modification. Problems resulting from leg length discrepancy often do not manifest themselves until the later years when the body is less resilient.
How proper foot wear can address foot problems.
Once you know what type of foot you have, you should select shoes that compliment your feet. If you have a tendency to over pronate, look for a shoe designed for control. Typically it will have a straight last, substantial heel counter and firm mid sole (not a cushioned model). A shoe for normal feet will have a semi-curved last and moderate cushion. Supinators should choose shoes with a curved last and maximum cushioning.
Have your feet measured with a Brannock Device for overall length, arch length and width. Try on both shoes in several styles. Do the toe jam test. If your toes hit the front of the shoe it may be too short or too wide. If you wear orthotics, try the shoes with them in.
Select a shoe that is appropriate for your activity.
Running shoes are great for running and walking (in line), court shoe for lateral movements and aerobic shoes for indoor exercise. Replace your shoes often. Worn shoes contribute to foot problems. Running shoes are good for about 1,000 miles. Do not try to get extra miles, instead get new ones and use the old for around the house if you must. Many runners rotate a couple pairs to get longevity.
What are Custom Foot Beds and Orthotics and how do they work.
Custom footbeds and orthotics are inserts that go into the shoe to provide correction or accommodation for foot abnormalities. Footbeds/orthotics also enhance foot function and comfort in footwear. Designs may vary depending on the footwear to be worn and the type of correction required. Most modern designs are made from semi-rigid materials that work with the shoe to help the foot function as normally as possible. The foot can either be casted or an impression taken which serves as model for orthotic fabrication. Sport footbeds and orthotics are transferable into most shoes with a removable sock liner (insole). Dress shoes rarely have the volume for a full length design thus requiring a ¾ length device. Good footbeds and orthotics treat the problem, not just the symptoms.
How to Determine Your Foot Type
A simple method for determining if your foot is flexible or rigid is to take a comfortable stance on a bare floor (not carpet) with your feet apart at shoulder width. First, look at each foot to evaluate the natural arch height. Next, rotate you hips to the left until you cannot keep the ball of your left foot on the ground. Evaluate the arch height for the left and right foot compared to their natural arch height.
Rigid feet will not show a significant change in arch height. The flexible foot will have a significantly increased arch height on the left and a diminished arch on the right. Reverse the hip rotation. Again, the rigid foot will not exhibit a dramatic change in arch height while the flexible foot will now have increased arch height in the right foot and diminished arch on the left.
While the “normal” foot will exhibit flexibility in this test, some arch profile will be maintained when the foot is fully pronated, as the right foot is when the hips are turned to the left or the left foot is when the hips are turned to the right.