Many people have low back pain, hip pain, or an uneven gait. They rarely realize the true cause: one leg is shorter than the other. This condition is known as leg length discrepancy (LLD). Leg length discrepancy (LLD) describes a difference in the effective length of the lower limbs. A structural discrepancy results from an actual difference in bone length, while a functional discrepancy can occur when factors such as pelvic alignment, joint position, or soft-tissue tightness make one leg functionally appear shorter.

LLD happens when a bone problem or pelvic misalignment makes one leg seem shorter than the other. If left untreated, this imbalance can eventually strain the spine and joints. When a structural discrepancy is significant and causing symptoms or functional problems, limb-lengthening surgery may be one treatment option for correcting the underlying length difference.

At The Height Lengthening Institute, Dr. Shahab Mahboubian specializes in exactly this kind of case. He treats uneven leg length through both non-surgical care and surgical correction. If chronic pain has been part of your life without a clear explanation, a limb alignment evaluation may finally provide one. You can schedule an evaluation here to get an accurate diagnosis.

Structural vs. Functional Leg Length Discrepancy: What’s the Difference?

A structural leg length discrepancy is a true difference in bone length. It shows up in the femur or tibia on an X-ray. A functional leg length discrepancy works differently. Here, the bones are actually equal in length, but a tilted pelvis, tight muscles, or a stiff joint make one leg act shorter while standing or walking.

Treatment depends on the size of the discrepancy, symptoms, age, skeletal maturity, and functional impact. Shoe lifts may be appropriate for some structural discrepancies, while larger or more symptomatic differences may warrant surgical evaluation. Functional discrepancies are generally addressed by treating the underlying musculoskeletal cause.

Also Read: What Is the PRECICE Max System? A Look at the Next Generation of Limb Lengthening

Root Causes: Why Do Legs Grow Unequal in Length?

Structural leg length discrepancy can be congenital or develop later because of injury, infection, abnormal bone growth, or other conditions affecting the femur or tibia. In children, damage to a growth plate can alter growth on one side, while fractures that heal with shortening can create a discrepancy later in life.

Identifying the exact cause helps guide the right treatment plan. Doctors typically evaluate four main categories:

• Growth plate injuries: Damage to a child’s growth plate can slow or stop bone growth on one side.
• Healed fractures: A break that heals in a shortened position can leave a permanent length difference.
• Congenital or developmental conditions: Differences in limb development present from birth or childhood can result in unequal leg lengths.
• Bone infections or tumors: Conditions like osteomyelitis can damage the growth plate and interrupt normal bone lengthening.

Key Symptoms: How LLD Affects Your Stance, Gait, and Spine

An untreated leg length discrepancy rarely stays confined to the legs. Over time, the body compensates by shifting weight, tilting the pelvis, and changing posture. This places ongoing strain on the spine, hips, and knees. That is why many patients are treated for back pain for years without ever finding the actual cause.

These symptoms don’t appear all at once, they tend to build gradually. This is part of why the condition is so often overlooked. The effects of LLD vary considerably from person to person. A clinically meaningful discrepancy can alter gait and loading patterns, and in some patients this may contribute to persistent back, hip, or knee symptoms or increased joint stress over time.

• Uneven stride or limp: One leg swings or lands differently than the other, often noticed by others first.
• Chronic back, hip, and knee pain: Uneven weight distribution places extra load on one side of the body with every step.
• Compensatory spinal curvature: A meaningful leg length difference can contribute to pelvic obliquity and a compensatory spinal curve while standing.
• Early joint wear: Years of uneven loading can speed up cartilage breakdown in the hips and knees.

Experiencing chronic back or hip pain from uneven legs? Schedule a diagnostic evaluation with Dr. Shahab Mahboubian and find out what's really causing it.

Also Read: PRECICE Max for Leg Discrepancy Correction: What Patients Should Know

Diagnostic Standards: Accurately Measuring Leg Length Differences

To diagnose a leg length discrepancy, doctors use a combination of physical exams and imaging. This ranges from a simple tape measurement to a precise EOS 3D standing X-ray. A tape measure can give a quick estimate. Imaging can quantify a structural difference and help identify whether the discrepancy originates in the femur, tibia, or both. The findings are interpreted alongside the physical examination to distinguish a true bony discrepancy from functional contributors.

Dr. Mahboubian's diagnostic process relies on full-length standing X-rays. These map the leg's mechanical axis, joint angles, and precise bone length. This detailed view shows exactly where the gap comes from, whether it is the femur, tibia, or both, and how the body has compensated over the years.

Treatment Solutions: From Non-Surgical Lifts to Surgical Equalization

Smaller discrepancies can often be managed without surgery, particularly when symptoms are mild. Options may include observation, shoe lifts, and treatment of associated functional problems. For larger or more symptomatic structural discrepancies, surgical correction may be considered after evaluating the amount of shortening, its cause, skeletal maturity, functional limitations, and the patient's goals.

For a permanent solution, the PRECICE® internal magnetic nail offers a frame-free alternative to older external fixators. The process begins with a small, controlled cut in the shorter bone. A magnetic nail is then placed inside the limb. Guided by an external remote, the nail gradually lengthens the bone by about 1 millimeter each day until both legs reach equal length.

Because the lengthening mechanism is internal, PRECICE avoids the external frame and pin sites associated with traditional external fixation. However, limb lengthening still requires close follow-up, rehabilitation, and monitoring throughout bone formation and recovery.

Also Read: PRECICE Max (PMax) Weight-Bearing: What Patients Should Know

Conclusion: Take the First Step Toward Symmetry

Uneven legs and chronic pain don’t have to be a permanent condition. It could be due to a childhood growth plate injury, a healed fracture, or a condition present from birth. Today’s diagnostic tools can locate the precise source. Small gaps may only need a shoe lift, while larger gaps may need PRECICE® lengthening. Either way, your particular situation will determine the best course of action.

Before anything else, the gap itself needs to be diagnosed, not just worked around or masked. A proper evaluation can indicate whether your gap is structural or functional. It also shows which treatment approach fits best. This is exactly what Dr. Shahab Mahboubian and The Height Lengthening Institute do. They employ advanced imaging and modern surgical techniques to restore lasting balance. If a leg length difference is affecting how you walk or contributing to ongoing symptoms, an evaluation can clarify the cause and whether treatment may help.

FAQs

1. How do I know if I have a structural or functional leg length discrepancy?

A structural discrepancy is a true difference in bone length as measured by full-length standing X-rays. A functional discrepancy occurs when the legs are the same length, but one leg appears shorter because of a tilted pelvis or tight muscles.

2. Can a leg length discrepancy cause chronic lower back and hip pain?

Yes. Just a small gap of 1 to 2 centimeters can change your pelvis alignment and change how you walk. This can cause the spine to tilt, weight to be unevenly distributed, joints to wear out faster, and eventually chronic back, hip, and knee pain.

3. How much of a leg length difference may require surgical correction?

There is no single measurement that automatically means surgery is necessary. Smaller discrepancies are often managed without surgery, while larger structural differences may warrant surgical evaluation when they cause meaningful gait problems, pain, or functional limitations. Age, skeletal maturity, the cause and location of the discrepancy, and the patient's goals also influence the treatment decision.

4. How does surgical limb lengthening fix an uneven leg length?

After the nail is placed, an external remote controller gradually lengthens it according to a surgeon-directed schedule. The lengthening phase depends on how much correction is needed and is followed by a longer consolidation period while new bone matures. Physical therapy and regular imaging are important throughout recovery.

5. Is surgery for leg length discrepancy covered by insurance?

Insurance coverage for leg length discrepancy surgery varies by plan and depends on factors such as the diagnosis, severity of the discrepancy, functional impairment, medical necessity criteria, and documentation. The Institute can help patients determine what information their insurer requires after an evaluation.

6. Why choose Dr. Shahab Mahboubian for leg length discrepancy correction?

Dr. Shahab Mahboubian is a fellowship-trained orthopedic surgeon in Los Angeles who specializes in limb lengthening and deformity correction. His approach uses detailed evaluation and modern internal lengthening techniques to develop an individualized correction plan based on each patient's anatomy, discrepancy, and functional needs.