Leg Length Discrepancy in Children: Causes, Diagnosis & Treatment

What Is Leg Length Discrepancy in Children?

Leg length discrepancy (LLD), also known as limb length inequality or anisomelia, is a condition where one leg is shorter than the other. While almost everyone has some degree of asymmetry, clinically significant differences that may require treatment occur in about 1 in 1000 children.

Leg length discrepancy is one of the most common orthopedic findings in children. Studies have shown that between 40-70% of the general population has some degree of leg length difference, though the vast majority of these are minor and have no clinical significance. The condition becomes medically relevant when the difference is large enough to cause functional problems, pain, or cosmetic concerns.

The condition can be classified in several ways. Structural LLD involves an actual difference in bone length, where the femur (thigh bone), tibia (shin bone), or both are physically shorter on one side. Functional LLD, on the other hand, occurs when the bones are actually equal in length, but other factors such as muscle tightness, joint contractures, or pelvic obliquity create the appearance of unequal leg lengths. This distinction is important because treatment approaches differ significantly between the two types.

The impact of leg length discrepancy depends largely on its magnitude. Differences of less than 2 centimeters rarely cause noticeable symptoms in children. The body has remarkable ability to compensate for small asymmetries through subtle adjustments in gait, posture, and pelvic positioning. However, as the discrepancy increases beyond 2 centimeters, compensatory mechanisms become less effective, and children may develop symptoms including limping, fatigue, and pain in the legs, hips, or back.

Types of Leg Length Discrepancy

Understanding the type of leg length discrepancy is essential for determining the appropriate treatment approach. Structural leg length discrepancy involves an actual anatomical difference in bone length. This can affect the femur, tibia, or both bones. The difference is measurable on X-rays and CT scans and represents a true skeletal asymmetry that will persist unless addressed through intervention.

Functional leg length discrepancy, by contrast, creates the appearance of unequal leg lengths despite bones of equal length. Common causes include muscle tightness (particularly the hip flexors or hamstrings), joint contractures limiting range of motion, pelvic obliquity from scoliosis or other spinal conditions, and foot or ankle deformities. Functional LLD often improves with physical therapy, stretching, and treatment of the underlying cause.

What Causes Leg Length Discrepancy in Children?

Leg length discrepancy can be congenital (present at birth) or acquired later in childhood. Congenital causes include developmental limb deficiencies and conditions like hemihypertrophy. Acquired causes include growth plate injuries from fractures, bone infections, tumors, and neuromuscular conditions like cerebral palsy.

The causes of leg length discrepancy in children are diverse and can be broadly categorized into congenital and acquired conditions. Understanding the underlying cause is crucial because it influences the prognosis, treatment options, and the likelihood that the discrepancy will change over time as the child grows.

Congenital causes are present at birth, even though they may not become apparent until the child begins walking or the difference becomes more noticeable with growth. These include developmental limb deficiencies where one leg simply develops shorter than the other, often with no identifiable cause. Hemihypertrophy (or hemihyperplasia) is another congenital condition where one side of the body grows faster than the other, affecting not just the leg but potentially also the arm and face on the same side. Congenital femoral deficiency and fibular hemimelia are specific conditions involving underdevelopment of the thigh bone or calf bone respectively.

Acquired causes develop after birth and can occur at any point during childhood. Growth plate (physis) injuries are among the most common acquired causes. The growth plates are areas of developing cartilage at the ends of long bones where growth occurs. Damage to these delicate structures from fractures, infections, or other trauma can cause the affected bone to grow more slowly or stop growing entirely. Approximately 10% of all childhood fractures involve the growth plate, and some of these result in growth disturbances.

Congenital Causes

Developmental limb deficiencies represent a spectrum of conditions where limbs do not form completely during fetal development. These can range from mild shortening to more severe deficiencies. In many cases, the exact cause remains unknown, though genetic factors, vascular accidents during development, and environmental factors have all been implicated.

Hemihypertrophy affects approximately 1 in 86,000 children and involves overgrowth of one side of the body. Children with this condition require careful monitoring not only for leg length issues but also for associated conditions including Wilms tumor, a childhood kidney cancer that has increased incidence in hemihypertrophy. Regular ultrasound screening is typically recommended.

Acquired Causes

Growth plate injuries from fractures are the most common acquired cause of leg length discrepancy. The distal femur (lower thigh bone) and proximal tibia (upper shin bone) are particularly vulnerable areas. Salter-Harris type fractures, which specifically involve the growth plate, carry the highest risk of subsequent growth disturbance. The risk increases with the severity of the injury and with injuries that cross through the growth plate.

Bone infections (osteomyelitis) can damage the growth plate if not treated promptly and effectively. The infection causes inflammation that can destroy the delicate cartilage cells responsible for bone growth. Bacterial infections are most common, with Staphylococcus aureus being the predominant organism. Septic arthritis of the hip in infants is particularly concerning because it can damage the blood supply to the femoral head and growth plate.

Neuromuscular conditions like cerebral palsy, poliomyelitis, and other conditions affecting muscle function can lead to leg length discrepancy through altered loading and use of the limbs. Bones respond to mechanical stress by growing, and a leg that is less used or has abnormal muscle forces acting on it may not grow as rapidly as the unaffected limb.

What Are the Symptoms of Leg Length Discrepancy?

Symptoms of leg length discrepancy include visible limping, one hip appearing higher than the other, compensatory knee bending, toe-walking on the short side, and pain in the legs, hips, or lower back. Many children with small discrepancies have no symptoms at all.

The symptoms of leg length discrepancy vary considerably depending on the magnitude of the difference and how well the child's body compensates for it. Many children with differences of less than 2 centimeters have no noticeable symptoms and may be unaware of any asymmetry. These small discrepancies are often discovered incidentally during examinations for other conditions or routine check-ups.

As the discrepancy increases, symptoms become more apparent. Parents often first notice that their child has an uneven gait or limp, particularly when the child is tired. The pelvis may appear tilted, with one hip sitting higher than the other when standing. Some children compensate by flexing the knee of the longer leg or walking on their toes on the shorter side to level the pelvis.

Pain is a common symptom in children with significant leg length discrepancy. The asymmetry creates abnormal mechanical stresses on joints and soft tissues. Lower back pain is particularly common as the spine attempts to compensate for pelvic obliquity. Hip pain can occur on either side - on the longer leg side due to increased impact forces, or on the shorter leg side due to muscle strain from compensation. Knee and ankle pain may also develop over time.

Signs Parents May Notice

Parents are often the first to recognize that something may be different about their child's walking pattern or posture. Common observations include the child limping, especially toward the end of the day when fatigue sets in. Clothing may fit unevenly, with pant legs appearing different lengths or waistbands sitting crooked. Shoes may show uneven wear patterns, with one shoe wearing out faster than the other.

When the child stands, parents may notice that one shoulder appears higher than the other, or that the child consistently stands with their weight shifted to one side. During walking, the child may seem to bounce or sway more than expected. Some children develop a compensatory scoliosis (curvature of the spine) that may be noticed when looking at the child from behind.

Long-term Complications

Untreated significant leg length discrepancy can lead to several long-term complications. Compensatory scoliosis develops as the spine curves to keep the head centered over the pelvis despite the uneven foundation. While functional scoliosis from leg length discrepancy is usually less severe than structural scoliosis, it can still cause back pain and postural problems.

Abnormal joint mechanics over time can accelerate wear and potentially contribute to early-onset osteoarthritis in the hips, knees, or spine. The abnormal loading patterns stress cartilage, ligaments, and other joint structures in ways they are not designed to handle. Studies have shown increased rates of degenerative joint disease in adults who had uncorrected leg length discrepancy during their growing years.

When Should You Seek Medical Care?

Consult a healthcare provider if you notice your child has a visible limp, uneven hips, complaints of leg or back pain, or if shoes wear unevenly. Early evaluation allows for proper monitoring and timely treatment if needed. Your pediatrician can refer you to a pediatric orthopedic specialist for comprehensive assessment.

Knowing when to seek medical evaluation for suspected leg length discrepancy can be challenging for parents. While many children have minor asymmetries that are perfectly normal and require no intervention, certain signs should prompt a medical consultation. Early evaluation is important because treatment options and their optimal timing depend heavily on the child's age and remaining growth potential.

You should contact your child's healthcare provider if you observe a persistent limp that doesn't resolve within a few days of rest. A limp can have many causes, and while leg length discrepancy is one possibility, other conditions should be ruled out. Similarly, if one of your child's hips consistently appears higher than the other when standing, this warrants evaluation.

Pain complaints should always be taken seriously. While growing pains are common in children, pain that is persistent, localized to one side, or associated with activity changes should be evaluated. Pay attention if your child starts avoiding activities they previously enjoyed or seems to fatigue more quickly than their peers during physical activities.

How Is Leg Length Discrepancy Diagnosed?

Diagnosis involves clinical examination using blocks to measure apparent leg length, followed by imaging studies. Scanogram X-rays provide precise measurements of femur and tibia lengths. Bone age X-rays of the hand help determine skeletal maturity and predict remaining growth, which is essential for planning treatment.

Accurate diagnosis of leg length discrepancy requires a systematic approach combining clinical examination with appropriate imaging studies. The diagnostic process aims to answer three key questions: How big is the discrepancy? What is causing it? How much will it change as the child continues to grow?

The clinical examination begins with observation of the child's gait. The examiner looks for limping, excessive pelvic tilt, compensatory knee flexion on the longer side, or toe-walking on the shorter side. With the child lying down, the examiner can perform several measurements. The apparent leg length is measured from the umbilicus to the medial malleolus (inner ankle bone), while the true leg length is measured from the anterior superior iliac spine (front of the hip bone) to the medial malleolus. Differences between apparent and true measurements can indicate pelvic obliquity or hip contractures.

The block test is a practical clinical tool where blocks of known thickness are placed under the short leg while the child stands until the pelvis appears level. The total height of blocks needed provides an estimate of the functional leg length difference. While less precise than radiographic measurements, this test reflects the functional discrepancy the child experiences in daily activities.

Imaging Studies

X-ray imaging provides precise measurements of bone lengths and is essential for surgical planning. The scanogram (or orthoroentgenogram) is a specialized X-ray technique that captures the entire length of both lower limbs on a single image, allowing accurate comparison of femur and tibia lengths on each side. This measurement has excellent reproducibility and typically agrees within 2-3mm between measurements.

Bone age X-rays involve imaging the left hand and wrist and comparing the appearance of the bones and growth plates to standardized atlases. The bone age may differ from the child's chronological age and is crucial for predicting remaining growth. Children with delayed bone age have more growth remaining than their chronological age would suggest, while those with advanced bone age have less. This information is essential for timing surgical interventions.

CT scanograms are occasionally used when more precise measurements are needed or when there are concerns about rotational deformities that would affect standard X-ray measurements. CT provides accurate measurements regardless of positioning and can assess both length and rotation simultaneously. However, the higher radiation exposure means it is reserved for specific indications.

Predicting Future Discrepancy

One of the most important aspects of evaluation is predicting how the discrepancy will change as the child grows. This prediction guides treatment decisions, particularly the timing of surgical procedures. Several methods exist for growth prediction, with the Moseley straight-line graph and the multiplier method being among the most commonly used.

These prediction methods use the child's current leg lengths, bone age, and established growth charts to estimate final adult leg lengths and the predicted discrepancy at skeletal maturity. Regular follow-up measurements allow the predictions to be refined over time. Most orthopedic specialists recommend annual monitoring for children with significant leg length discrepancy until they reach skeletal maturity.

How Is Leg Length Discrepancy Treated?

Treatment depends on the severity of the discrepancy. Differences under 2cm may need only observation or shoe lifts. For differences of 2-5cm, epiphysiodesis (growth plate arrest surgery) on the longer leg can allow the shorter leg to catch up. Larger differences over 5cm may require limb lengthening surgery using external or internal fixation devices.

Treatment for leg length discrepancy is highly individualized, taking into account the magnitude of the discrepancy, the child's age and remaining growth potential, the underlying cause, and the child's and family's preferences. The goal is to minimize the discrepancy at skeletal maturity while avoiding complications and minimizing the impact on the child's activities during the treatment period.

For small discrepancies of less than 2 centimeters, treatment is often unnecessary. These minor differences typically do not cause symptoms, and the body compensates effectively. Some children may benefit from a shoe lift - an insert placed inside the shoe or a modification to the shoe sole that helps level the pelvis during standing and walking. Shoe lifts are simple, non-invasive, and can be adjusted as the child grows.

Conservative management with observation is appropriate for many children, even those with larger discrepancies, if they are asymptomatic. Regular monitoring allows the healthcare team to track how the discrepancy changes over time and intervene if and when needed. Physical therapy may be recommended to maintain flexibility, strengthen compensating muscles, and optimize gait mechanics.

Epiphysiodesis - Growth Plate Arrest

Epiphysiodesis is a surgical procedure that slows or stops growth at the growth plate of the longer leg, allowing the shorter leg to "catch up." This is the most common surgical treatment for leg length discrepancy in growing children and has a success rate exceeding 90% when properly timed. The procedure is less invasive than limb lengthening and has a shorter recovery period.

The surgery is performed under general anesthesia. The surgeon makes small incisions near the growth plate at the lower end of the femur, the upper end of the tibia, or both, depending on where growth arrest is needed. The growth plate is then destroyed using drilling or curettage techniques. In some cases, temporary methods using plates or staples can slow but not permanently stop growth, allowing for some reversibility if predictions prove inaccurate.

Timing is absolutely critical for epiphysiodesis. The procedure must be performed when the child has exactly the right amount of growth remaining to equalize leg lengths by maturity. If done too early, the previously shorter leg may end up longer. If done too late, the correction will be incomplete. Orthopedic surgeons use bone age X-rays and growth prediction charts to calculate the optimal timing.

Recovery from epiphysiodesis is relatively straightforward. Children typically go home from the hospital within one to two days after surgery. Initially, they walk with crutches to protect the surgical site, but most can bear full weight as pain allows. Return to normal activities usually occurs within a few weeks, and return to sports within two to three months. Regular follow-up X-rays monitor the correction as growth continues.

Limb Shortening Surgery

For skeletally mature individuals where epiphysiodesis is no longer an option, limb shortening can be performed on the longer leg. This involves removing a segment of bone from the femur, typically just below the hip joint. The bone is then stabilized with a plate and screws while it heals. This procedure is more invasive than epiphysiodesis and carries higher risks of complications, so it is reserved for specific situations where other options are not suitable.

Limb Lengthening Surgery

For larger discrepancies exceeding 5 centimeters, limb lengthening offers the possibility of substantially increasing the length of the shorter leg. This advanced surgical technique uses the body's natural ability to regenerate bone when it is slowly stretched apart. The procedure involves cutting through the bone (osteotomy) and then gradually separating the bone ends, typically at a rate of about 1 millimeter per day. New bone forms in the gap, eventually consolidating into normal bone.

Traditional limb lengthening uses external fixation devices - metal frames attached to the bone with pins that pass through the skin. Modern techniques increasingly use internal devices, either fully implantable lengthening nails or combination internal-external systems. Internal devices reduce the risk of pin site infections and may be more comfortable for patients, though they are not suitable for all cases.

Limb lengthening is a demanding treatment that requires significant commitment from the child and family. The lengthening phase typically takes several months, during which daily adjustments to the device are needed. The consolidation phase, where the new bone hardens sufficiently to bear weight, takes additional months. Throughout this period, intensive physical therapy is essential to maintain joint mobility and muscle strength. Complications can include joint stiffness, muscle contractures, premature or delayed bone consolidation, infection, and nerve or blood vessel issues.

How Can Children Manage Leg Length Discrepancy?

Most children with leg length discrepancy can participate fully in normal activities including sports. For those with symptoms, shoe lifts can improve comfort. Physical therapy helps optimize gait and maintain flexibility. Regular monitoring by a healthcare provider ensures any progression is identified early and treated appropriately.

Living with leg length discrepancy is manageable for most children, and many lead completely normal, active lives with minimal or no restrictions. The key to successful management is understanding that each child's situation is unique and requires an individualized approach based on the magnitude of the discrepancy, symptoms, and the child's activity level and goals.

For children with minor discrepancies, simply understanding that small asymmetries are normal and usually do not require treatment can be reassuring for both the child and parents. These children typically need no modifications to their activities and can participate fully in sports and physical education. Regular monitoring, usually annually, ensures that any changes are detected early.

Physical therapy plays an important role for children with symptomatic leg length discrepancy. A physical therapist can teach exercises to maintain flexibility in the hips, knees, and ankles, which may become tight as the body compensates for the asymmetry. Strengthening exercises for core and lower extremity muscles help optimize gait mechanics and reduce strain on joints. Therapists can also provide guidance on activity modification if certain movements cause discomfort.

Psychological Considerations

The psychological impact of leg length discrepancy should not be overlooked. Children may feel self-conscious about their limp or about wearing shoe lifts. They may worry about being different from their peers or about future limitations. Open communication between parents, healthcare providers, and the child is essential. Children should be given age-appropriate explanations about their condition and involved in treatment decisions when possible.

Support groups and connecting with other families dealing with similar conditions can be valuable resources. Knowing that others have successfully navigated the same challenges can provide reassurance and practical tips. For children undergoing lengthy treatments like limb lengthening, psychological support may be particularly important to help them cope with the demands of the treatment process.

What Is the Long-Term Outlook?

The prognosis for leg length discrepancy is generally excellent with appropriate management. Most children achieve good functional outcomes with minimal residual discrepancy. With proper timing, epiphysiodesis achieves results within 2cm of leg length equality in over 90% of cases. Even large discrepancies can be successfully corrected with limb lengthening.

The long-term outlook for children with leg length discrepancy has improved significantly with advances in diagnostic techniques and treatment options. Most children achieve excellent functional outcomes and go on to lead active, unrestricted lives as adults. The key factors influencing prognosis include the underlying cause of the discrepancy, the magnitude of the difference, the timing of interventions, and adherence to treatment recommendations.

For children who undergo epiphysiodesis, long-term studies show excellent outcomes. Over 90% of properly timed procedures achieve the predicted correction, with final leg length differences of less than 2 centimeters. These small residual differences are rarely symptomatic and do not typically require ongoing treatment. Importantly, there appear to be no significant long-term consequences of having had growth arrested at the growth plate - the bones heal normally and function without problems into adulthood.

Limb lengthening outcomes have also improved substantially with modern techniques and devices. While the treatment process is demanding, most patients achieve their lengthening goals and are satisfied with the results. Long-term follow-up studies show that the lengthened bone remodels to normal structure and strength over time. Joint function is typically preserved when appropriate physical therapy protocols are followed.

Even without surgical intervention, children with small to moderate leg length discrepancy who are managed with observation or shoe lifts generally do well. Studies examining adults who had untreated leg length discrepancy as children show that many have no significant symptoms or functional limitations, particularly for differences under 2-3 centimeters.