Leg Length Differences

There have been many studies to show that there is frequently a difference in one leg as compared to the other. Statistics range from as low as 40 percent to as high as 93 percent of the subjects examined have a leg length difference or asymmetry. In my own statistical analysis of over 1000 runners I have found over 90 percent have a difference in leg length Of 1/4 inch or more. This figure is consistent with major studies performed by other investigators such as Klein and Pearson, who examined in independent studies students in large numbers from elementary through high school. The significance of this rather common finding is important in our overall evaluation and, hopefully, successful treatment of patients with problems from running. One of the most important things we look for when we examine a patient is symmetry; that is, how equal are the measurements of one side as compared to the other. In our examination we compare such things as leg rotation, rear and forefoot motion, ankle joint motion and leg length. Too often practitioners do not measure leg length; or, if they do, they do not consider it to be important enough to treat. In my opinion this is an error.

If most of us have a difference in leg length, then why do I feel that it is so important to treat it? Our bodies have an amazing ability to accommodate or compensate for small differences between our right and left halves, leg length being just one of these differences. Runners with chronic repetitive stress magnify this difference dramatically. This increased stress or loading on the legs can cause the runner to develop an injury or overuse problem. Dr. Stephen Subotnick, a well known sports podiatrist and author, terms this loading problem the "rule of three". In walking, one times the body weight is transmitted through the support leg. In running it is three times the forces. Thus, a biomechanical abnormality in running is three times that of walking. For example, a 1/4" leg length difference in a non athlete can function like a 3/4" difference in a runner, with devastating results. With few exceptions, symmetry is essential to proper function in the athlete.

Causes
While there are many individual causes of leg length differences, we can categorize them as one of three types: structural, functional, or a combination of both.

The structural type relates to the actual shortening of one or more bones. This is a real or anatomical short leg. It is important to under stand that this shortening can affect other areas of the body, such as the hip, back, shoulders and neck. For example, on the short leg side the hip will be lower, the back will be curved towards the long leg side (scoliosis), and the shoulders will tilt toward the long side.

A functional leg length discrepancy is a result of abnormal positioning of the leg in the hips, muscle imbalances, abnormal leg rotations, or faulty foot function. This type of leg length discrepancy has the same appearance as the structural leg difference.

The third type, the combination, is actually the most common as pointed out in the study by Okun, Morgan, and Burns. They concluded that the great majority (89 percent) of their sample who had a leg length discrepancy actually had a combination structural functional deformity.

Other causes often overlooked must also be discussed. What I term environmental causes are of a major concern. These include but are not limited to the road, sidewalk or track where the training is done. Everyone appreciates the slope of the road or sidewalk depending on whether you are going with or against traffic. This slope or unevenness can result in an environmental effect on the leg structure. For example, when running in the street against traffic the right leg will be higher than the left. When running on the sidewalk against traffic the right leg will be lower than the left. Interestingly, we have seen some patients who have felt more comfortable running on a particular surface in a particular direction. Our examination has found that their short leg syndrome was accommodated by the surface that they were running on. Conversely, we have found patients with a leg length discrepancy have made their condition worse by running on the wrong side of the road or sidewalk.

Also the shoe can play a major part in leg length discrepancies. The quality of the running shoes and how they wear or breakover may also be a factor in unequal leg length.

Effects
Leg length differences are the cause of many problems associated with running, especially in the low back and upper leg. It has also been associated with outside knee pain and ankle sprains. Statistically, we see a correlation between these complaints and the short leg. My findings, consistent with other published studies, show that in 80% of the cases the short side will be associated with the aforementioned problems. That is not to say that all conditions are caused by short leg syndrome. A careful examination is needed to determine the cause of the problem. Low back pain or sciata (pain running down the back of the leg), may be due to nerve route compression from the spinal column, nerve disease or other causes. Other medical consultations may be necessary.

Diagnosis
Many different methods can be used to determine if there is a leg length difference. A simple method to do at home is to stand barefooted on a firm surface with both feet together looking into a full-length mirror. Next, place the end of the index finger on the high point on the front of both sides of the hip bone. They both should be at the same level. If not, you have a leg length difference.

Another observation can be made at the same time. While standing erect, knees straight, look at the arches of your feet. They should both be the same. If one is lower than the other then you probably have a long leg on the low arch side. The reason for this is the body will attempt to compensate for the leg length difference by pronating (flattening) the arch of the foot on the long side and supinating (raising) the arch on the short side. You can also lie down, and have a friend look at the bottom of both of your feet. If the heel-sole of one foot is lower than the other, suspect a leg length difference.

When we examine for a leg length difference we use many sophisticated techniques including tape measurements from different body areas, physical examination, and even special x-ray views. From a clinical point of view, I rarely find it necessary to know to the "millimeter" the difference in leg length. A good biomechanical exam is usually sufficient. We recently have been using the Electrodynogram at SportsMedicine Grant. This computer, which measures the forces on the foot and leg structure, can detect leg length discrepancies.

I have also found that a side view x-ray of the foot bones can often detect a leg length discrepancy. We commonly compare the inside ankle bones by measuring from the hip to the inside of the ankle. Although they may be equal, there is still a "short leg " Oftentimes, this shortness is caused by alterations of the structure within the foot itself. This structural change of the foot causes a functional difference in the length of the leg.

Treatment
It would seem that if an individual had a short leg syndrome, the natural treatment would be simply to add a lift of appropriate thickness to the heel of the shoe. It isn't so easy. Let me state, before reviewing my treatment methods, that the literature as well as my personal communications with allopathic, osteopathic, and chiropractic professionals reveals significant differences in their approach to treatment. The allopathic professional basically uses lift therapy, while the osteopathic profession concentrates on the use of manipulative measures and lift therapy where it is indicated. Chiropractic medicine also concentrates on manipulation primarily. I feel Podiatric medicine uses lift therapy when indicated but goes beyond by also addressing rearfoot and forefoot compensation and total lower extremity mechanics.

To understand the Podiatric treatment we must remember the classification of leg length discrepancies; anatomical, functional, or combinations. However, regardless of the cause, what is important is that the pelvis be level during stance. Conversely, a heel lift or orthotic used incorrectly can create an overuse problem or weakness and, therefore, should be avoided.

Basically, a structural leg length difference is treated with only a simple heel lift. This is done by using 1/16 inch calibrated blocks that are added underneath the heel until the pelvis is level. Individuals with scoliosis (spine curvatures) when standing that disappear when sitting have a functional leg length discrepancy. If the scoliosis persists with sitting, it may be the cause of the leg length difference.

The use of heel lifts can also vary greatly among specialists. Some recommend using the full amount of the difference while others use only 1/2 that amount. When the difference is an inch or more I prefer to use a formula that provides a full lift in the heel. l/2 that amount under the ball of the foot, and 1/4 of that under the toes. This seems to work better then a full thickness lift throughout the entire sole. If it is less than one inch but greater than 1/2 inch it can be incorporated into the shoe and a neutral orthotic device. Less than 1/2 inch can easily fit into most shoes without much difficulty.

The function leg length difference is often the result of muscular spasm or even more commonly caused by abnormal foot function. Heel lifts alone in these cases are not enough. An orthotic must be used to control abnormal foot function, most commonly excessive proration or inward rolling of the foot. If this excessive proration is controlled on the affected side it may level out the pelvis and preclude the necessity to even use a lift. However, in most instances, the foot structure must be controlled and a lift used. Combination problems are also thus treated by an orthotic plus a lift.

Summary
When diagnosed and treated properly, symptoms from leg length discrepancies can transform a runner with chronically disabling problems into a pain-free individual. Many of our results have been dramatic. We have treated patients who have had nagging problems for long periods of time, who have tried all types of shoes, physical therapy, stretching and strengthening exercises, and even orthotics without satisfactory relief. If after evaluation, one of the three types of leg length discrepancies is found, the treatment and subsequent relief of symptoms has been more than satisfactory. Sometimes it involves just adding a lift, other times a lift fabricated with an orthotic. Let me express one word of caution in the treatment of leg length discrepancies, especially if they are functional or combinations. A lift on the "short" side may relieve the muscular spasm causing the leg length difference. This will cause the difference to disappear and the lift then is no longer needed. If the lift is left in place it can cause the shift of symptoms possibly to the opposite leg and be the cause of unwanted problems. Therefore, appropriate follow-up evaluation is mandatory when using lifts or orthotics. The best time for reevaluation is two to three weeks following the initial use of the lift, since it normally takes that long for the body to adapt to the forces applied by the device.

I have a few patients whose leg length seems to shift back and forth in relatively short periods of time. It is almost impossible to keep them con trolled and without symptoms. I have been successful in treating these patients by dispensing heel lifts that can be shifted from one shoe to the other, depending on their symptoms. I have also made some interesting observations regarding leg length differences. While over 90% of my patients have some type of leg length difference, over 80% of the time their problem is on the long side. I feel that this is a result of the longer leg having to absorb more shock but not being able to do so. I also have observed that the long leg, as opposed to the short leg, is usually more externally or outwardly rotated in the body's attempt to compensate for its extra length.

While the causes of leg length differences are many, I feel most are a combination of structural and functional with the majority of these changes being demonstrated in the foot structure. Lateral or side view x-rays clearly demonstrate the accommodation in the joints of the foot structure.

The importance of proper diagnosis cannot be overstressed. There are many causes of symptoms of stress in the back, legs and feet ranging from inflammatory changes, disc disease, to faulty foot structure. Referral for consultation to the appropriate specialist may be needed as well as specialized laboratory and x-ray tests. As with all conditions, it is of utmost importance to ascertain what the problem is. Once discovered, treatments as simple as a heel lift can be surprisingly dramatic.