One leg being shorter than the other, medically termed Leg Length Discrepancy (LLD), is a condition where a person’s lower limbs are of unequal lengths. This difference can vary from a minor, barely noticeable variation to a significant disparity affecting daily activities.
While a slight difference is common and often causes no problems, larger discrepancies can impact posture and movement. This condition can arise from various factors, influencing how the body functions and adapts over time.
Defining Leg Length Differences
Leg Length Discrepancy (LLD) is categorized into two primary types: True (Structural) and Apparent (Functional). True LLD involves an actual difference in the length of the bones within the leg, typically the femur (thigh bone) or tibia (shin bone). This structural variation means one leg’s skeletal components are physically shorter than the other.
In contrast, Apparent LLD occurs when the bones themselves are equal in length, but one leg appears shorter due to issues outside the bones. This perceived difference often stems from problems in the pelvis, spine, or surrounding soft tissues. The body may compensate for an underlying issue, leading to an apparent shortening of one limb without changes to the bone structure.
Causes of True Leg Length Discrepancy
True Leg Length Discrepancy can stem from several underlying causes that directly affect bone growth or structure. Some individuals are born with conditions that lead to unequal leg lengths, known as congenital conditions, such as hemihypertrophy or bone deficiencies like fibular or tibial hemimelia.
Developmental issues during childhood can also contribute to true LLD. Injuries to the growth plates (epiphyseal plates) at the ends of long bones, which are areas of cartilage responsible for bone growth, can cause one bone to grow slower or stop growing prematurely. Certain bone diseases or dysplasias, such as Ollier disease or neurofibromatosis, can also disrupt normal bone development and lead to discrepancies.
Trauma is another common cause, particularly fractures that heal in a shortened position or involve the growth plates in children. Occasionally, orthopedic surgeries, such as hip or knee replacements, can result in a slight difference in leg length. Bone loss due to tumors or infections can also lead to a true leg length discrepancy.
Understanding Apparent Leg Length Differences
Apparent Leg Length Differences occur when the actual bone lengths are equal, but one leg appears shorter due to other bodily mechanics. These discrepancies typically involve issues with alignment, posture, or soft tissues rather than the bones themselves.
A common cause is pelvic obliquity, where the pelvis is tilted or rotated. This pelvic tilt can arise from various factors, including muscle imbalances. Scoliosis, a sideways curvature of the spine, can also contribute to an apparent leg length difference by affecting overall body alignment and leading to an uneven stance.
Muscle imbalances or contractures, particularly tightness or weakness in the hip or leg muscles, can pull the pelvis or leg out of proper alignment. Issues within the joints, such as the hip, knee, or ankle, can affect how the leg articulates, leading to a perceived difference. These factors cause the body to compensate, leading to an apparent difference even though the skeletal length remains the same.
Identifying and Managing Discrepancies
Leg Length Discrepancy can manifest through several noticeable signs and symptoms. Individuals might exhibit a limping gait or a change in walking style, often walking on their toes on the shorter leg. Other indicators include back pain, hip pain, or knee pain, as the body attempts to adapt to the unevenness. Uneven shoulder or hip heights and clothing that hangs unevenly can also suggest a discrepancy. Even minor differences, such as those greater than 10 mm, can lead to stress on the lower back and hips over time.
The potential impact of LLD extends beyond localized pain, as the body’s compensatory mechanisms can lead to strain and discomfort throughout the musculoskeletal system. For instance, a tilted pelvis due to an LLD can cause the lumbar spine to curve, leading to spinal strain. Untreated discrepancies, particularly larger ones, may contribute to premature joint degeneration, such as osteoarthritis in the hip or knee.
Management approaches for LLD vary depending on the type and severity. For minor true LLD or apparent LLD, non-surgical options are often pursued. Shoe lifts, either inserted inside the shoe or attached to the sole, can help equalize leg lengths and alleviate symptoms. Physical therapy and chiropractic care can address muscle imbalances and alignment issues common in apparent LLD, helping to relax tight muscles and improve posture.
For more significant true LLD, surgical interventions may be considered. In growing children, epiphysiodesis slows or stops growth in the longer leg’s growth plates, allowing the shorter leg to catch up. For individuals who have completed growth or have very large discrepancies, limb lengthening surgery can gradually extend the shorter bone. Alternatively, a section of bone may be removed from the longer leg to shorten it, particularly for discrepancies where the patient has stopped growing. Professional diagnosis is important to determine the most appropriate treatment.