The next 4 posts will be on limb length discrepancy and its place in a clinical biomechanical practice. If you are using orthotic devices, the lifts are placed under and up to 1/4 inch normally can fit in an athletic shoe along with the orthotic device. How do you get a reproducible understanding of their leg length? Initially we will teach them all the same (structural, functional, or combination), but there are many nuances. Tape measures are an unreliable method, mastered only by a few. Sitting or lying examinations tend to be great observations of pelvic tilts, but not structural limb shortages, as their reference is the spine to the pelvis. Matching your measurement/treatment to clinical changes of pain reduction and feelings of improved stability is the true answer if you are measuring accurately. The next post will go over the actual measurement techniques.
We always start our evaluation by watching a patient walk. The common signs that there may be a limb length discrepancy are head tilts (typically towards the short leg), shoulder drops (typically towards the long side), body lean or dominance to one side (typically the long side), uneven belt line (the most unreliable and the most difficult to obtain), asymmetric arm swing, and asymmetric pronation (higher degrees to the long leg). All the references to long or short side are merely general rules with plenty of exceptions. The photo below shows the dominance seen in a uncompensated short right side with the fall to the right, shoulder drop to the right, and head tilt to the right, so you see general rules should mean that you measure for limb length but not reliable enough to decide which leg is the longer one. However, limb dominance or lean is the first sign I observe when watching a patient walk.
The photo below shows the more classic presentation of head tilt towards the short leg and shoulder drop towards the long leg. Dominance, as shown above, is 80% to the long leg. As the shoulder drops to the long side to straighten the spine, the cervical spine will curve to the short side.
This is the classic S shaped curves that patients with leg length develop. The shoulder drops with the long leg and the head tilts to the short leg. The bottom of the curve is that the tilted pelvic causes the lumbar spine to move towards the short leg, and then. the thoracic spine to come back towards the longer side (an attempt to right the ship) dropping the shoulder on the long side.
This obvious left higher belt line documenting the long left side is actually not easy to obtain in clinical practice. It takes alot of effort getting the patient in the right clothes. I bow to you if you are normally successful. This is why limb dominance with shoulder and head tilts are currently more important to me.
With the pelvis off, and curves developing in the spine, arm swing can be a way for the body to balance things out. You see arms on one side much further from the body than the opposite side (typically on the nondominant or short side). You can see that the shoulder and arm swing is much more than the other side. This could mean that actually one arm is swinging less than the other side. We slow down arm or shoulder motion due to opposite side activity at the hips joints. Is the patient seeking stability for pain reduction or hip instability?
I will end our initial discussion on limb length discrepancy with asymmetrical foot motion. If one foot is pronating more than the other, even if actually one foot supinates more than the other, you are creating compensation for a structural long leg, or at minimum, creating a functional short leg on the more pronated side. Which side looks more everted or pronated to you? Next week, measurements!
