A Guide To Detecting And Treating Limb Length Discrepancy
Limb length discrepancy (LLD) can cause a variety of symptoms. There are a variety of common clinical techniques clinicians can use to help detect LLD. Radiographic imaging provides the best method for measuring LLD. Treatments vary but can lead to significant improvement of symptoms. Indeed, the detection and treatment of LLD can be a very satisfying aspect of a clinical biomechanics practice.
In cases of LLD, gait evaluation normally shows the dominance of one side or leg. As the patient walks down the hall, there is a tendency to lean to one side. One can see this on every step or every third or fourth step, but the lean is always to the same side. The head cups from center to the dominant side and then back to the center, but it does not go to the other side. The dominance may be to the longer or shorter side. The dominance to one side should disappear as one puts lifts in to correct LLD. Remember that dominance is a clue that a LLD may exist.
What is my normal standing examination? With the patient barefoot or shoeless, I palpate the anterior superior iliac spine (ASIS), the iliac crests (IC) and the greater trochanters (GT). Try to keep your fingers parallel to the ground as you find the same spot on each side. Sometimes, you will need to ask the patient if you and the patient are on identical spots. Especially when it comes to evaluating for LLD in obese patients, the ASIS is impossible to locate well. Crouching or kneeling to get one’s eyes level with the palpated landmark is vitally important.
Then one can place blocks of varying millimeters under the foot on the side considered shorter to seek evenness. It is great when all three landmarks show the same side is short. However, even then, it may take different heights to level the three landmarks. For example, a short left leg may show a 9 mm difference at the ASIS and a 6 mm difference at the greater trochanters and iliac crests.
One will often find a pelvic asymmetry. For example, one may see the IC high on one side, the ASIS low on that side, and the GT high, low or level. It is important to keep in mind that these quick clinical screens are just that. Fortunately, one can routinely determine the dominance in gait after the standing exam and start treatment at the first visit. When one notes pelvic asymmetry, radiographic evaluation is usually necessary. Be advised that tape measure examination is very inaccurate.
What Should You Look For In The Gait Analysis?
Leg or side dominance in gait is a useful clue that a LLD may exist. While watching the patient walk, see if one or more of the following occur.
• Head leans to one side
• Shoulder drops to one side
• Arm swing is greater on one side
• Arm position is further from body on one side
• More asymmetrical excessive pronation on one side
These findings are the basis of gait analysis for LLDs. There are several common patterns with LLDs.
Pattern A: Typical adult pattern (long left leg noted)
• Head leans/tilts to the left
• Shoulder drops to the left
• Trunk mass leans to the left
• Arm swing is greater on the right
• Arm position is further from the body on the right
• Excessive foot pronation on left
Pattern B: Typical youth pattern (long left leg noted)
• Head leans/tilts to the right
• Shoulder drops to the right
• Trunk mass leans to the right
• Arm swing is equal or greater on either side (right or left)
• Arm position is further from the body on the left
• Excessive foot pronation is equal or greater either side (right or left)
Understanding these two common patterns is easy if you call pattern A “compensated” and pattern B “uncompensated.” The complexity comes in recognizing partially compensated patterns and the involvement of pelvic asymmetries and scoliosis.