Leg length discrepancy (LLD) is a common condition where one leg is noticeably shorter than the other, impacting a person’s gait, posture, and overall body mechanics. The difference can range from a fraction of an inch to several centimeters. While minor discrepancies may not cause symptoms, larger ones can lead to compensatory movements that strain the hips, knees, ankles, and spine. Understanding the cause and magnitude of the difference is the first step toward effective management. Treatment options vary widely, from simple shoe inserts to complex surgical procedures.
Distinguishing Different Types of Leg Length Discrepancy
Leg length discrepancies fall into two primary categories. Structural LLD, also known as anatomical LLD, involves an actual physical difference in the length of the bones, typically in the femur or tibia. This type of discrepancy can result from congenital issues, severe fractures that healed improperly, or conditions that affect the growth plates in childhood. Functional LLD occurs when the bones themselves are equal in length, but a difference is created by issues above the leg, often referred to as apparent LLD. This can be caused by muscle imbalances, joint contractures in the hip or knee, or a pelvic tilt that makes one leg seem shorter when measured clinically. Because the underlying cause is mechanical rather than bony, functional LLD usually responds well to non-surgical treatments focused on restoring alignment and muscle balance.
Diagnostic Methods for Accurate Measurement
Accurately quantifying the discrepancy is a necessary step before any treatment plan can be established. Medical professionals often begin with clinical methods, such as using a tape measure to compare the distance between specific bony landmarks or using calibrated blocks placed under the shorter foot. These clinical assessments serve as useful screening tools but are not always as precise as imaging methods. Radiographic imaging provides the most objective and detailed measurement of structural LLD. A full-length standing anteroposterior X-ray, sometimes called a teleoroentgenogram, captures the entire lower extremity from hip to ankle in a single or stitched image. The scanogram or CT scanogram is another highly reliable imaging technique, which uses point-to-point measurements of the femur and tibia to calculate the exact difference in bone length, often minimizing image magnification errors.
Conservative Management Strategies
Conservative approaches are the first line of management, particularly for structural discrepancies under 2 centimeters (20 mm) and are often the primary treatment for functional LLD. These non-invasive methods aim to equalize the leg length or address the underlying mechanical cause. The most common intervention for mild structural LLD is the use of shoe modifications to raise the height of the shorter limb.
Shoe Modifications
Shoe lifts, insoles, or orthotics placed inside the shoe are frequently used for smaller differences, typically 5 to 10 millimeters. These devices compensate for the length difference, promoting better pelvic and spinal alignment and reducing mechanical stress. When the discrepancy is larger, a full external shoe modification may be necessary, where the sole and heel of the shoe are built up to accommodate the required height.
Physical Therapy
Physical therapy plays a significant role, especially in managing functional LLD and the compensatory issues arising from structural LLD. For functional discrepancies, treatment focuses on manual therapy techniques, stretching, and strengthening exercises to correct pelvic obliquity and muscle tightness. Gait training is another component, which helps patients adapt to walking with a corrected lift or retrain proper movement patterns. Addressing imbalances in the hip flexors, hamstrings, and core muscles can often resolve the apparent shortening seen in functional LLD without the need for an orthopedic lift.
Surgical Interventions for Correction
Surgical correction is typically reserved for substantial structural leg length discrepancies, generally those exceeding 2 to 2.5 centimeters, or when conservative measures have failed to alleviate pain or functional limitations. The two main surgical strategies involve either lengthening the shorter limb or shortening the longer limb. The decision on which procedure to use is based on the magnitude of the difference, the patient’s age, and their skeletal maturity.
Limb Lengthening
Limb lengthening procedures are used for larger discrepancies. These involve a controlled process called distraction osteogenesis, where the bone is surgically cut in a procedure called an osteotomy. A device, either an external fixator or an internal magnetic rod, is then used to gradually pull the bone segments apart by about one millimeter per day. This slow, continuous distraction encourages new bone formation, known as callus, in the gap, effectively increasing the limb’s length.
Shortening Procedures
Shortening procedures are an alternative, especially for adults with moderate discrepancies who have finished growing. Acute shortening involves removing a segment of bone from the longer leg and then stabilizing the remaining bone with plates or rods. In children and adolescents who are still growing, a procedure called epiphyseodesis can be performed. This involves surgically manipulating the growth plates (physes) of the longer leg to slow down its growth, requiring careful timing to ensure the legs equalize by the time the child reaches skeletal maturity.