Types and Prevalence of LLD
There are two types of leg length discrepancies: functional and anatomical. A functional leg length discrepancy refers to a musculoskeletal imbalance where any number of structures (or muscles) in the body are not working as they should. This results in parts of the skeleton being pulled out of alignment making it appear as though one leg is shorter than the other. Alternatively, an anatomical leg length discrepancy occurs when the bone(s) in one leg are actually shorter/longer than those in the other (Knutson, 2005). As the possible cause(s) of a functional leg length discrepancy are wide and varied, this article will focus on anatomical leg length discrepancies and how they affect your client’s body.
Anatomical, also known as true, leg length discrepancies have been found in as much as 95% of the population (Pappas and Nehme, 1979). However, significant leg length discrepancies of more than one (1) cm are found in about 1 out of 4 people (Knutson and MacEwen, 2005). True leg length discrepancies affect the entire musculoskeletal system and play a substantial role in the health, function and experiences of pain for your clients (McCarthy, 2001).
How LLDs Affect the Body
The body is designed to be dynamic and can adjust incredibly well to varying movements and positions. However, a true leg length discrepancy (that is left untreated) causes bones and joints to shift out of alignment, soft tissue structures like muscles, tendons, ligaments and fascia to compensate/overwork and can lead to pain and injury over time (Price, 2010). Some major areas of the body that are affected by a LLD discrepancy are the lower back, hips, feet and ankles.
LLD and the Lower Back:
The pelvis forms the base of support for the spine. Therefore, a level and well-balanced pelvis is critical for spine health and optimal lower back function. In order to comprehend how an LLD can affect the spine and lower back, it is imperative to understand the structural anatomy of this area. Either side of the pelvis is made up of three bones (i.e., the ilium, ischium and pubis) that are fused together (Gray et al., 1995). However, independent movement of each side of the pelvis is possible due to two important joints located in the pelvis. One of these joints is called the sacroiliac joint (SI joint). The SI joints are located on either side of the back of the pelvis where the top of the pelvis (i.e., the ilium) meets the base of the spine (i.e., the sacrum). The other joint is located on the front of the pelvis where the pubic bones (i.e., pubis) meet (i.e., the pubic symphysis) (see picture below) (Gray et al., 1995). Since the base of the spine articulates with each side of the pelvis via the sacroiliac joint, movement of the pelvis affects movement and function of the spine.
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