Not A Leg To Stand On
It will surprise you to know that only 1 in 4 people in the world with two legs actually have two the same length as one another. In the majority of cases the difference in measurement between the two is miniscule and the individual will likely go their entire life not having knowledge of the anomaly as well as not being affected by it. Differences in length of over 2cm are rare.
Here we are going to look at the most common health issues suffered by athletes caused by leg length discrepancy (LLD).
Symptoms and Causes
As a professional or sports coach, it should be first assumed that a back pain or lower leg discomfort in the client may well be a symptom of leg length discrepancy and a leg length asymmetry issue. Leg length asymmetries appear to be the third most common cause of running injuries and occur in 60 to 90 percent of the population.
With regards to classifying leg length discrepancy, there are two primary categories: structural and functional.
The one minor contributor is environmental.
Structural discrepancies result from an anatomic shortening of the bones or lower extremities caused by a growth plate injury in childhood or adolescence, fractures and/or genetic and acquired conditions that affect bone growth. Structural leg length differences can also be caused by a spinal abnormality such as scoliosis.
Functional leg length differences usually occur as a result of muscle weakness or inflexibility at the pelvis or foot and ankle complex. They include pelvic obliquity, adduction or flexion contractures of the hip, genu varum, valgum or recurvatum, calcaneovalgus, equinovarus and rearfoot pronation.
Environmental factors such as drainage crowns built into roadways, banked running surfaces, and excessive wearing of shoes can create a situation that replicates a leg length difference. These environmental factors can also either accentuate or correct structural and functional length differences depending on how the athlete is running.
Leg length asymmetry causes the centre of gravity to be shifted to the short leg side. Most commonly, the compensations associated with limb length asymmetry include
- pelvic tilt (to the short side),
- lumbar scoliosis (convex to the short side),
- knee flexion (increased on the long side),
- genu recurvatum (on the short side),
- subtalar joint pronation (on the long side),
- ankle plantar flexion
- foot supination (on the short side).
The most common symptom associated with LLD is backache.
Other symptoms affecting the lower extremity with a structural discrepancy usually appear first on the long leg side and include flank pain, arthritis of the knee, psoasitis, arthritis of the hip, patellar tendinitis, patellofemoral pain syndrome, plantar fasciitis, medial tibial stress syndrome and metatarsalgia.
Symptoms affecting the short extremity include iliotibial band syndrome with lateral knee pain, trochanteric bursitis, sacroiliac discomfort, Achilles tendinitis and cuboid syndrome.
If the patient just has a functional LLD, the symptoms will usually appear on the short side first and include plantar fasciitis, medial tibial stress syndrome, patellofemoral pain syndrome, illiotibial band syndrome, ipsilateral sacroiliac discomfort with contralateral low back pain, and secondary psoasitis.
Diagnosis and Solutions
When it comes to ruling out LLD, examinations must be organised and systematic so not to overlook any clues that are suggestive and consistent with a short leg.
To assess for asymmetry, palpate the iliac crests while the patient is standing. Be vigilant of a pelvic side shift, lateral spine curvature (noting the convexity), frontal plane leg deviation (genu varum and valgum), sagittal plane leg deviation (hamstring and/or ankle equinus), transverse plane leg deviation (excessive femoral anteversion demonstrated by “squinting patella”), and/or unilateral foot pronation.
If any of these are present, it must be noted whether it is occurring on the patients left or right.
The next procedure is to perform gait analysis so to evaluate for asymmetries during ambulation. Dynamic gait analysis findings should support static measurements. Evaluations of the three cardinal body planes (frontal, sagittal, and transverse) while looking at each body segment.
Analysing the head and neck for any tilt to one side or the other. It is common to see a tilt to the short side. Evaluation of the shoulders for any tilt and awareness that the most common is to see tilts to the long leg side for balance. Note the arm swing for symmetry of motion. The spine needs to be examined for any curvatures or deviations. The patient’s hips should be observed for any asymmetries in motion as the hip will drop to the short side. Evaluation of his or her knees for any varum, valgum, flexion or recurvatum. The position of the heel makes to the ground at contact should be noted and his or her mid-stance as there is usually an increase in heel eversion on the long side.
Since LLD produces an asymmetry, the timing of the gait parameters will also be deviated. An early heel off on the short side. The long side will have a shortened swing phase while the short side will have a longer swing phase. The long side will have a longer stance phase while the short side will have a shorter stance phase of gait.
Once identified LLD, categorise the asymmetry as a structural or functional problem.
- A structural short leg manifests as a pelvic obliquity in which the iliac crest is low on the same side and becomes level with the use of a heel lift.
- A functional short leg secondary to foot pronation manifests as a pelvic obliquity in which the iliac crest is low on the same side and becomes level by placing the subtalar joint in neutral position.
The pronation test will highlight whether it can determine its effect in contributing to the LLD.
- Have the patient stand with his or her knees extended and the feet in the angle and base of stance.
- Have him or her place the subtalar joint in the neutral position.
- Palpate the iliac crests and record any discrepancies.
- Allow the patient to pronate.
- Re-evaluate the iliac crests as to their position and note any changes.
Performing this test helps determine one of three conclusions:
- Pronation has no effect on limb length
- Pronation is causing a functional short leg
- Pronation is compensating for the long leg
Depending upon the findings, the pronation test will enable a decision whether orthoses or heel lifts are indicated in treating the LLD.
If subtalar joint pronation has no effect on limb length, there will be no change between the iliac crests with neutral and pronated subtalar joint positions.
If the iliac crest on the ipsilateral side is lower in pronation than in neutral subtalar joint position, then the subtalar joint pronation is causing a functional leg length asymmetry.
In this situation, an orthosis with appropriate posting would be indicated to correct the LLD. If the iliac crest becomes more level when examined in the pronated position, then subtalar joint pronation is compensating for a structural LLD.
Using a heel lift on the opposite extremity is indicated in this instance to correct the anatomic asymmetry along with decreasing the amount of compensatory long leg subtalar joint pronation.
How To Determine The amount of LLD
Once diagnosed and classified this can be quantified in the discrepancy by either a direct or indirect method of measurement.
The direct method involves measuring the distance between the anterior superior iliac spine to the medial malleolus. Unfortunately, the direct method is difficult to reproduce and fails to take into account functional LLDs.
The indirect method is superior to the direct method. The indirect method of limb length evaluation involves reducing the pelvic tilt and leveling the sacral base by placing a material of a known thickness under the short leg while the patient is standing. The indirect method is reproducible and accurate in quantifying the amount of leg length discrepancy. In some cases, it may be required to confirm the diagnosis with a roentgenograph.
Top treatment insights for LLD often depends on whether or not symptoms are present. If the body is compensating for a length difference without causing biomechanical stress in other areas, correcting the difference may alter the patient’s body mechanics in such a way as to cause an injury.
If the discrepancy is causing symptoms, you do need to address it in order for a full recovery to take place. Treatment also depends on the classification of the asymmetry. If your patient has a functional asymmetry due to unilateral foot pronation, it can be corrected by emphasising a properly posted orthotic.
When it comes to environmental asymmetry secondary to improper footwear or canted running surfaces, a recommendation can be made for new or appropriate foot gear or a change in the geometry of the running surface.
Heel lifts can be used to treat structural limb asymmetry. The purpose of the heel lift is to level off the sacral base and correct the compensatory scoliosis caused by the short leg. It can be determined the amount of heel lift needed via the indirect method of evaluating a structural shortage.
Again, have the patient stand with his or her subtalar joint in neutral. A material of a known thickness should be placed under the short limb until the iliac crests are level. The thickness of the heel lift under the short leg is the amount of the patient’s limb length inequality. Initially, the amount of heel lift should be about half of the anatomic discrepancy because the superstructure is being realigned in a gradual manner. With feedback from the patient, it can determined the final amount of lift that will produce the best results regarding the underlying symptoms.
Approximately a 1/4- to 3/8-inch heel lift can fit into the average adult shoe. If more correction is required, the patient may need an addition to the outside of the shoe.
If you suffer from leg length discrepancy or know someone who does, foot orthotics from The Foot and Leg Clinic could be the solution you are looking for and appropriate treatment could help alleviate the pain.