How To Evaluate For Leg Length Discrepancy

Author(s): 
By David Levine, DPM, CPed

Small, seemingly inconsequential leg length differences (LLD) can lead to symptomatic biomechanical asymmetry. Without careful examination, subtle LLDs can go undetected as can the etiology of the pathology they create. Differences in leg lengths vary from the subtle to the obvious. Once one identifies LLD, practitioners also need to know how to treat it. Understanding the patient’s lifestyle and activity level will help you determine when to address his or her LLD.
Whether it is a difference in appearance of the two feet or a difference in function, asymmetry is often obvious if we know what to look for and why to look for it. For example, a patient may present with hallux limitus. While there are many causes of hallux limitus, if the finding is asymmetric and no trauma was involved in the deformity, then looking for a LLD would be worthwhile.
Another example is assessing the range of motion within each foot. If there are joints that move or feel different between feet, then a LLD may be present. Since the foot is the mobile adapter for the body, it will compensate for the differences more proximally. Asymmetry is often the first clue that the patient has a LLD. Understanding the prevalence of LLD and how these differences can contribute to pathomechanics will yield important clues in helping you provide successful treatment outcomes for your patient’s biomechanical problems.
Addressing the injured joint or chief complaint only without looking at the interrelationship between the injury and the rest of the body can allow some problems to slip by without being properly identified. The injury, ache or pain may improve with the prescribed treatment, but then may resurface if the underlying cause is a LLD that was not properly identified. This may then lead to a pattern of injuries, injuries that may perhaps affect one side of the body from the back down to the foot. The LLD assessment can be an easy addition to your biomechanical exam. Integrating this assessment into your diagnostic work-up will yield beneficial results.

There are many types of LLD such as congenital, developmental and acquired. Congenital leg length discrepancies can have several causes with the most common one being hemihypertrophy. This condition involves one side of the body developing faster than the other. This is an isolated finding most of the time but can, in some instances, affect the kidneys as well. Other causes of LLDs in children include trauma, neurologic conditions and talipes equinovarus. When there is significant LLD in children, leg lengthening procedures (including recent advances in external fixation) are within the realm of possibility for some patients.
When one sees LLD among adult patients, it may be due to leftover differences that were never addressed or identified at a younger age, arthritic processes and surgery such as joint replacement.
LLDs can be a challenge to treat, but even more challenging to identify. The challenging cases are not necessarily those that have a large difference from one side to the other. In these cases, the difference is usually known and of longstanding duration. Fine-tuning may be needed but these patients come in with the awareness and knowledge that a difference exists. The more challenging cases are the adults of any age who come in with a mechanically related chief complaint that needs to be solved.
One of the best ways to determine whether a LLD is present is to ask the patient. Since your patient is the one who has the difference, a little savvy prompting and asking the right questions will give you important clues. Does the patient favor one leg over the other when standing? Does the patient find it generally uncomfortable to stand? Do certain activities such as washing dishes aggravate the condition? If the answers to these questions provide information consistent with an imbalance, then you know where to direct your examination.

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