Have you ever wondered if you have a short leg? Perhaps you have heard the phrase “your legs are off.” Maybe you have been told “one leg is longer than the other.” The concept of leg length discrepancy, or anisomelia, is commonly overused or used inaccurately. LLD is considered an orthopedic condition appearing in childhood as a congenital condition or resulting from a previous injury or illness. Most people have some small degree of limb length discrepancy, but dramatic differences can alter your ability to participate in a variety of activities.
An illness or injury that causes damage to the bone's growth plate can also lead to the development of a limb length discrepancy, or short leg syndrome, later in life. A leg length discrepancy can cause a visible limp or make it difficult for a child to participate in age-appropriate physical activities. When the difference is greater than 1.5 to 2 centimeters (5/8 inch) in length, evaluation with an XR scanogram is recommended to specifically measure the length of each of the bones of the legs. A leg length discrepancy that falls into this category can require treatment with custom shoes and/or surgical lengthening.
Causes of limb length discrepancy can be divided into four main groups:
• When the cause of LLD is congenital, it usually appears at birth, the length of the discrepancy is greater than acquired LLD and it progresses over time.
• Developmental LLD results from a childhood illness or a growth plate injury; developmental cases result in a discrepancy that appears over time, as the injury or illness slows the growth of the injured or diseased limb.
• Fractures and other traumatic injuries to the bone may heal incorrectly, causing one leg to be shorter than the other; however, in some cases, these injuries can also speed up the growth of the injured leg.
• Both bone tumors and the treatments designed to eradicate them can affect bone growth. This is especially true if the illness happens in infancy.
There are three types of limb length discrepancy (LLD) related to the four previous causes.
Anatomical or structural limb length discrepancy is a physical (bone) shortening of one lower limb between the top of the femoral (thigh bone) and the ankle.
Functional or non-structural shortening is a one-sided asymmetry of the lower extremity without any shortening of the thigh or shin bones. A functional inequality may occur at any level of the lower extremity. There are different causes that may lead to a functional inequality: foot mechanics, adaptive shortening of soft tissues, joint contractures, ligamentous laxity and mal-alignments. This is the type of LLD that is most commonly misapplied. Patients are told they have “one leg shorter or longer than the other” without appropriate explanation.
Environmental LLDs are only significant for a small number of high-level athletes or specialized occupational job tasks. As an example: accumulation of forces during running when a runner consistently trains on one side of a crowned road. Environmental cases of LLD can easily be solved by asking the runner to run on the opposite side then they usually do. Environmental LLD is often considered a form of functional LLD.
The nonsurgical intervention is mainly used for the functional and environmental types of leg length discrepancies. Non-surgical intervention consists of stretching and strengthening the muscles of the legs. The most common muscles to stretch and strengthen are the tensor fascia latae, adductors, hamstrings, piriformis and hip flexor muscles.
The use of shoe lifts also belongs in the category of nonsurgical intervention. These shoe lifts consists of either a shoe insert (up to 10-20 millimeters of correction), or building up the sole of the shoe on the shorter leg (up to 30-60 mm of correction). This lift therapy should be implemented gradually in small increments over time.
Several studies have examined the treatment of low-back pain patients with LLD with shoe lifts. While several studies have shown promising results, with patients experiencing decreased lower back pain, the overall evidence in the scientific literature is still inconsistent.
Two factors dictate if intervention is needed or not: the magnitude of the inequality and whether or not the patient is symptomatic. It has been suggested to divide limb length inequality into three categories: mild (0-30 mm), moderate (30-60 mm) and severe (more than 60mm). In addition, it has been suggested that mild cases should be treated conservatively unless the patient is symptomatic, then a surgical approach may be considered. Moderate cases should be treated on a case-by-case basis, but surgical intervention is high on the list. Severe cases should strongly consider surgical correction.
If you are ever told that one leg is shorter than the other or your “hips are off,” your response should be, “Which bone is short?” or “What do you mean by my hips are off?” Always get a more detailed explanation of what you are being told.