Detecting And Treating Leg Length Discrepancies
Essential Diagnostic Tips
When it comes to ruling out LLD, your exam must be organized and systematic so you don’t 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 on the lookout for 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 you see any of these, be sure to note whether it is occurring on the left or the right.
Proceed to perform gait analysis so you can evaluate for asymmetries during ambulation. Dynamic gait findings should support static measurements. Evaluate the three cardinal body planes (frontal, sagittal, and transverse) while looking at each body segment. Analyze the head and neck for any tilt to one side or the other. It is common to see a tilt to the short side. Evaluate the shoulders for any tilt and be aware that it is most common to see tilts to the long leg side for balance. Note the arm swing for symmetry of motion.
Also be sure to evaluate the spine for any curvatures or deviations. Watch the patient’s hips for any asymmetries in motion as the hip will drop to the short side. Evaluate his or her knees for any varum, valgum, flexion or recurvatum. Keep an eye on the position the heel makes to the ground at contact and his or her midstance as there is usually an increase in heel eversion on the long side.
Since LLD produces an asymmetry, you’ll find the timing of the gait parameters will also be deviated. You may notice 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 you’ve identified LLD, you need to categorize 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.
What The PronationTest Will Tell You
You can use the pronation test to 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 you see.
Performing this test helps you determine one of three conclusions:
• pronation has no effect on limb length;
• pronation is causing a functional short leg; or
• pronation is compensating for the long leg.
Depending upon your findings, the pronation test enables you to decide 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 you examine it 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.