Last month we discussed abnormal pronation of the foot and its relationship to running injuries. We saw that when this excessive motion is caused by structural malalignments of the foot itself, orthotics can be helpful. But, we also stated that abnormal foot movements are not always the result of joint dysfunctions of the foot alone, but may in fact be stemming from another area, in which case orthotics may be of little value. So let’s see what these are and what can be done about them to promote normal foot mechanics and thus prevent possible injury.
Due to the interlocking structure of the ankle joint, the motions in the foot which we have described as pronation/supination are transmitted upward through the entire lower extremity as internal/external rotation respectively. This is what we call an “obligatory motion,” meaning we have no choice in the matter. And, it helps explain how abnormal foot movements can cause overuse injuries in areas outside the foot, since they will cause abnormal leg movements as well. But what goes up may also come down, meaning that if there are abnormal leg movements you might end up with abnormal foot motions. Why would you have abnormal leg movements?
Many times, faulty lower extremity mechanics are caused by abnormalities in the structure of the long bones themselves. For instance, the angle of the neck of the femur may be greater than normal which will cause excessive internal rotation of the hip. Other times the problem may be due to muscular imbalances which foster rotation of the leg too much in one direction. These problems are complex and not easy to identify in many cases, especially by the runner him/herself. And, oftentimes there are limitations to what can be done through exercise to correct them, particularly those that involve the bones exclusively. There are some muscular problems which very often cause abnormal pronation which can be readily self-identified and treated through exercise and which all runners should pay close attention to in terms of prevention
According to one study of 1200 runners at the Louisiana State University Medical Center’s Runners’ Clinic from 1978-83, 80% of the injured runners showed signs of hamstring contractures(tightness). Achilles tendon contractures affected 40%. Both conditions, especially the tight calf muscles, play a major role in causing compensatory overpronation due to their limiting effect on the available motions at the knee and ankle joints. It is the subtalar joint of the foot which helps make up this difference, but at the cost of excessive pronation.
The good news is that you can easily test yourself for these deficiencies and, if present, correct them without professional intervention. The best way to assess hamstring flexibility is as follows: Sit at the edge of a table or chair with your lower back absolutely upright and “at attention.” Put one hand in the small of your back and feel the curve inward. Now, straighten one knee slowly. If you are unable to completely straighten your leg without losing the inward curve of your lower back, your hamstring length is deficient.
To test for calf tightness, sit on the floor with one leg out straight, the other bent at the knee comfortably. Place a belt around the ball of the foot of the straight leg and pull the ends of the belt towards you, taking care to keep the foot from going out to either side. If the bottom of your foot does not go at least 10-degrees past the perpendicular to the floor, your calf muscles are tight.
The nice thing is that the tests described here can be used as the treatment to stretch these muscles. Simply do them by holding each for 10-15 seconds, 10 times each, twice daily, without causing yourself any pain. These exercises are effective primarily because they isolate so well the desired muscles, but perhaps more important, they are the safest way to increase flexibility in these areas.
Next month, the discussion of biomechanical causes of injuries continues with “The Myth of Leg Length Discrepancy.”
