Detecting And Treating Leg Length Discrepancies
Chronic overuse problems that persist despite appropriate care are the hallmarks of a leg length discrepancy (LLD) in an athlete. While the symptoms associated with LLDs are diverse and, at times, vague and confusing, you should suspect limb length asymmetry when athletes have back or lower extremity complaints. Leg length asymmetries appear to be the third most common cause of running injuries and occur in 60 to 90 percent of the population. In regard to classifying LLD, the two major categories are structural and functional. The one minor category is environmental. Structural discrepancies result from an actual anatomic shortening of one or more of the bones of the lower extremity. This can occur from a growth plate injury during childhood or adolescence, fractures or genetic and acquired conditions that affect bone growth. Structural leg length differences can also result from spinal abnormalities such as scoliosis. Functional leg length differences usually occur as a result of muscular 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 mimicks 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 on a given surface. Know The Compensations And Symptoms Of LLD The spine, pelvis and lower extremity are all involved in the compensation of leg length asymmetry. Leg length asymmetry causes the center 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), and ankle plantar flexion and 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. 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.