Leg length discrepancy (LLD), also known as anisomelia, is a condition where one leg is shorter or longer than the other. This difference can range from subtle to several inches. While minor variations often cause no issues, significant discrepancies can affect well-being and daily activities. LLD is a common condition. Understanding LLD involves recognizing its forms, how it impacts the body, and available management approaches.
Types and Causes
Leg length discrepancy is broadly categorized into two main types: structural and functional. Structural LLD involves an actual physical difference in the bone lengths of the lower extremities. This type can be congenital, originating from birth where bones may not develop fully (e.g., congenital femoral deficiency or fibular hemimelia). It can also be acquired through factors like injuries to growth plates in children, which are areas of cartilage responsible for bone growth, disrupting normal development. Bone fractures, particularly those that heal in a shortened position, are another common cause in both children and adults. Certain diseases, such as bone infections (osteomyelitis) or tumors, can also affect bone growth and contribute to structural LLD.
Functional LLD, in contrast, occurs when the leg bones themselves are of equal length, but an apparent difference arises from issues elsewhere in the body. This type is often linked to misalignments or imbalances that affect posture and mechanics. For instance, a pelvic tilt, where the pelvis is not level, can create the appearance of one leg being shorter. Muscle imbalances or tightness in the hips, back, or legs can also contribute to functional LLD by altering body alignment. Foot mechanics, such as excessive pronation (flattening of the arch), can also lead to an apparent leg length difference by affecting how the body distributes weight and maintains symmetry. Functional LLD can also stem from joint contractures or neuromuscular conditions that impact posture and movement.
Recognizing the Signs and Potential Effects
Individuals with leg length discrepancy often exhibit a range of physical signs and may experience various symptoms as their body attempts to adapt. An observable limp or an altered walking pattern, known as gait abnormalities, is a common indication, especially with more significant differences. People might walk with a head or neck tilt, drag their feet, or take shorter steps. Postural changes are also frequently seen, such as uneven shoulders or hips, or a tilted pelvis. A person might unconsciously shift their weight to one side or stand unevenly, leading to uneven wear on shoe soles.
The body employs various compensatory mechanisms to manage the length difference, which can lead to discomfort and pain. The shorter leg might compensate by toe-walking or increasing ankle plantarflexion, while the longer leg may increase hip and knee flexion. These compensations place uneven stress on joints and muscles, often resulting in pain in the lower back, hips, knees, or ankles. The pain can sometimes travel up and down the leg, particularly after physical activity. Functional scoliosis, an abnormal curvature of the spine, can also develop as the body tries to maintain balance, and over time, the continuous effort to compensate can lead to increased fatigue and contribute to degenerative conditions like osteoarthritis in the hip and knee joints.
Addressing Leg Length Discrepancy
Healthcare professionals diagnose leg length discrepancy through a comprehensive evaluation that typically begins with a physical examination. During this examination, the doctor might observe the patient’s walking pattern to identify any gait abnormalities and check for postural issues like a tilted pelvis or scoliosis. A common technique involves placing blocks of different heights under the shorter leg until the pelvis appears level, allowing for an estimation of the discrepancy. Imaging studies, particularly X-rays or specialized scanograms, are used to obtain precise measurements of the bone lengths, confirming structural differences. Computed tomography (CT) scans can also provide detailed images, especially in cases with contractures.
Management and treatment approaches for LLD are individualized, considering the type, severity, and the patient’s age and overall health. For minor discrepancies, particularly those less than 2 centimeters, conservative methods are often effective. Shoe lifts or orthotics are a common non-surgical intervention, designed to equalize the leg lengths by adding height to the shoe of the shorter leg. These can be internal inserts or external modifications to the shoe sole, with external lifts typically used for discrepancies over 10 millimeters. Physical therapy plays an important role, focusing on stretching tight muscles, strengthening weaker ones, and improving overall body mechanics and posture.
For more significant discrepancies, or when conservative treatments are insufficient, surgical interventions may be considered. In growing children, a procedure called epiphysiodesis can be performed to slow or stop the growth of the longer leg, allowing the shorter leg to catch up over time. This procedure requires careful timing to achieve the desired outcome. For larger discrepancies or in adults where growth plates are closed, limb lengthening surgery is an option. This involves surgically cutting the bone (osteotomy) and then gradually pulling the two bone segments apart, a process called distraction osteogenesis, which encourages new bone formation. This gradual lengthening is typically done at a rate of about one millimeter per day. Internal devices, such as telescopic rods placed inside the bone, or external fixators, can be used to facilitate this process. Surgical options aim to restore more balanced leg lengths, potentially improving gait, reducing pain, and enhancing overall quality of life.