Subtle Discrepancies Between the Lower Extremities May Cause Back Pain

The human body is a pretty symmetrical structure. This is even truer in regards to the musculoskeletal system. The right leg usually equals the left leg in length, and they both try to keep the pelvis nicely squared and parallel to the ground. This maintenance of symmetry is important for efficient function of the spine and pelvis in the gait cycle (walking and running). They are very important supporting structures involved in weight transmission. Asymmetry or deformity may cause unequal distribution of muscle forces. These forces can cause tilt in the pelvis and compensatory changes in the spine to adjust to the deformity.

In a tilted pelvis, the deformity may be above or below the pelvis. If it is below, the deformity may come from unequal limb length. The difference in limb lengths may be due to various reasons. The most common reasons are post traumatic overgrowth and angular deformities. A condition above the pelvis, called mild scoliosis, may also cause the pelvis to tilt leading to similar pain.

These discrepancies, even though subtle in the beginning, may gradually reduce the strength of the balancing forces over time. Initially, the musculoskeletal system tries to compensate for the deformity. As the flexibility and compensation decreases, the abnormal loading of the joints may cause manifestations of pain syndromes. Studies have shown postural consequences of these subtle limb length discrepancies over time. The abnormal loading of the joints and unequal distribution of muscle forces have been attributed to the development of disc herniations, facetogenic pain, sacroiliac joint pain, trochanteric bursitis, and pelvic obliquity causing scoliosis and hip arthritis. Recent studies have shown that the bigger the deformity or asymmetry, the greater the chances are that these pain syndromes will manifest earlier.

These pain syndromes can be easily diagnosed through clinical examinations often complemented with injections. Diagnosing and explaining the underlying deformity and how it causes the pain syndrome to the patient helps to avoid frustration and the development of chronic pain.

These pain syndromes and compensatory deformities can be prevented by recognizing the problem early and maintaining a healthy lifestyle with exercise. If the pain is constant, the pain cycle can be broken with some injections. Injections can further complement the ongoing physical therapy. If these changes have already caused arthritic issues, surgeries like sacroiliac joint fusion, facet rhizotomies, or limited minimally invasive lateral fusion at the apex of the curve can be done.

Our musculoskeletal system works in synchrony. Any deformity in any part of the weight bearing axis will influence the other compensatory muscles and joints. This forces them to work more and decreases overall endurance and efficacy of gait. A limb length discrepancy after any fracture or joint replacement may cause pain syndromes in the back and SI joint which can be treated if diagnosed early.

At Prairie Spine, we have engrained these concepts in our comprehensive evaluations. This helps us to diagnose reasons for your pain and tailor optimal treatments directed towards the pain generator.

Article written by Dr. Amit Bhandarkar M.B.B.S., M.S., M.D., Orthopedic Spine Surgeon at Prairie Spine.


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