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Pediatric Leg Length Discrepancy and Surgical Limb Lengthening

October 15, 2025:

For many parents, noticing that one of their child’s legs appears shorter than the other can be both confusing and concerning. While a small difference in leg length is common and often harmless, a more significant difference—known as leg length discrepancy (LLD)—can affect the way a child walks, runs, and grows. The good news is that pediatric orthopaedic specialists have a range of safe and effective treatment options to help restore balance and function. From careful observation and growth-modulating procedures to advanced surgical limb lengthening, modern treatments are designed to support healthy development and keep kids active, comfortable, and confident.

What is Leg Length Discrepancy (LLD)? 

Pediatric leg length discrepancy is a condition where one of a child’s legs is noticeably shorter than the other, affecting overall skeletal balance and function. It can impact a child’s mobility, posture, and long-term musculoskeletal health. Understanding the nature and causes of leg length discrepancy is the first step toward effective treatment—which may include non-surgical options, growth-modulating procedures, or, in some cases, the life-changing potential of surgical limb lengthening.

Types of Leg Length Discrepancy

  • Structural LLD: A difference in the actual length of the leg bones (femur or tibia). This is the most direct form, characterized by a measurable difference in the length of the major leg bones.
  • Functional LLD: The bones are equal in length, but the legs appear different due to factors such as muscle imbalance, joint contracture, or misalignment in the hip or knee that changes the position of the foot.

Symptoms of Leg Length Discrepancy (LLD)

  • Limping or an unusual gait
  • Waddling
  • Uneven posture, often with a noticeable tilt in the pelvis or a dropped shoulder on one side
  • Localized and Referred Pain: Constant physical compensation strains the body causing chronic discomfort or pain in the back, hip, knee, or ankle

Causes of Pediatric Leg Length Discrepancy (LLD)

Pediatric Leg Length Discrepancy is not a single disease but rather an outcome of various underlying issues that affect the growth plates or the bone structure itself.

Issues can include:

  • Congenital defects – fibular hemimelia (absence of fibula bone) congenital short femur and hemiatrophy (absence of one side of the body parts)
  • Bone infections that damage growth plates
  • Fractures by trauma that affect bone growth
  • Tumors or surgical removal of bone tissue requiring reconstruction
  • Growth plate injuries
  • Other medical conditions affecting muscles, nerves, or blood flow that indirectly impact bone development

Diagnosis of Leg Length Discrepancy (LLD)

Accurately diagnosing Leg Length Discrepancy (LLD) is the first step toward planning effective treatment. Diagnosis is performed by a specialized pediatric orthopaedic surgeon utilizing both clinical expertise and advanced imaging to determine the precise nature and extent of the discrepancy.

  • Medial history to learn details of your child’s developmental milestones, past injuries, infections, and any family history of orthopaedic issues to pinpoint the potential origin of his/hers Leg Length Discrepancy (LLD for a precise diagnosis and tailored treatment plan.
  • Comprehensive physical examination to assess gait, posture, spinal alignment, and the relationship of the pelvis to the lower limbs.
  • X-rays for accurately measuring the length of the major bones to obtain precise measurements This imagery is crucial for calculating the exact amount of discrepancy and determining the specific bone(s) responsible.
  • Tumors or surgical removal of bone tissue requiring reconstruction
  • MRI or advanced imaging: In complex cases, MRI helps assess soft tissues, growth plates, and underlying causes of LLD.

Growth Modulation and Epiphysiodesis

Not every child with a leg length difference requires a full limb-lengthening procedure. When a child still has growing years remaining, your pediatric orthopaedic surgeon may recommend growth modulation or epiphysiodesis—minimally invasive procedures that guide or balance growth instead of replacing it.

Epiphysiodesis

Epiphysiodesis involves slowing or temporarily stopping growth in the longer leg by targeting the growth plate (epiphysis). As the shorter leg continues growing, the difference gradually decreases.

  • The timing is carefully calculated based on your child’s remaining growth.
  • It’s typically performed through small incisions with minimal downtime.
  • Most children return to regular activities soon after surgery..

Growth Modulation

Growth modulation techniques use small plates, screws, or implants to gently guide bone growth and alignment. They can also correct angular deformities such as knock knees or bow legs. Once the correction is achieved, the implants are removed.

When Recommended

Growth modulation and epiphysiodesis are most effective for children who are still growing and whose leg length difference is projected to be less than 5 cm (about 2 inches) at skeletal maturity. They may serve as:

  • A definitive treatment for smaller discrepancies
  • Or a staged part of a global treatment plan, reducing how much lengthening will be needed later

Advantages

  • Minimally invasive
  • Short recovery and minimal scarring
  • Preserves natural bone growth
  • May reduce or eliminate the need for future lengthening surgery

What is Surgical Limb Lengthening?

Once the surgery has been performed and the healing phase initiated the lengthening process begins externally. Bone lengthening begins a few days or weeks after the surgery. The child (or parents) uses a small handheld remote controller placed against the skin over the rod. This device utilizes powerful magnets to slowly and non-invasively activate the internal gear system. This controlled gradual distraction pulls the two segments of the bone apart by a minuscule amount several times a day (often less than a millimeter total per day). This tension stimulates the body’s natural regenerative powers to grow new healthy bone tissue (a process called distraction osteogenesis) in the gap achieving the desired limb length. X-rays are obtained every 2 to 3 weeks to check for new bone growth, nerve and muscle function.

Consolidation Phase (Healing) Phase

Surgical limb lengthening is a controlled, gradual process designed to correct a deformity, straighten a limb, or replace missing bone. This advanced procedure uses innovative internal lengthening devices that allow the bone to grow safely and precisely over time.

The process begins with placement of a specialized expandable rod inside the bone. Inside the rod is a magnetic gear system, secured with screws to keep the device stable. The incisions are then closed with stitches.

Distraction (Lengthening) Phase

After surgery and initial healing, lengthening begins. Using a handheld magnetic remote placed on the skin, the internal gear system is activated to gently pull the two bone segments apart by less than a millimeter per day. This gradual movement stimulates new bone growth (called distraction osteogenesis) in the gap.

  • X-rays every 2–3 weeks monitor bone growth and ensure muscles and nerves adapt safely.

Consolidation (Healing) Phase

The Consolidation Phase is a lengthy healing period. Once the target length is reached adjustments to the lengthening device are stopped. The newly formed bone called regenerate, is initially soft and weak. It requires continuous support to prevent bending or fracture. Depending on the initial technique used, the support structure is managed during this phase. * Internal and External Fixators each offers a distinct approach to achieving skeletal correction
  • External Support If an external frame was used for the distraction phase (often in a technique like Lengthening Over Nails, or LON) the frame remains in place until the bone is deemed stable enough for the next step.
  • Internal Stabilization: Once the distraction phase is complete, the external frame is typically removed. An internal rod a permanent implant is placed within the bone to provide long-term support. This rod acts as an internal splint, allowing the new bone to harden and calcify fully around it.
  • Internal Devices: For fully internal lengthening systems, the function of the rod automatically ceases once the programmed length is achieved, and it then serves as an internal scaffold for the duration of the consolidation phase.
  • Removal of the External Fixator: The removal of the external fixator device is performed under general anesthesia. After removal, a cast made of plaster of Paris (POP) is placed for a month for protection.

Bone Healing

Physical therapy (PT) is a vital part of recovery. It helps maintain joint motion, strength, and flexibility throughout the process. Most children can gradually return to full activity—including sports—about 6 to 12 months after the initial procedure, once cleared by their surgeon.

Leg length discrepancy can range from a mild difference to a significant imbalance that affects walking, posture, and confidence. The good news is that modern pediatric orthopaedic care offers many effective solutions—from growth modulation and epiphysiodesis to advanced surgical limb lengthening—tailored to each child’s age, growth, and goals. With expert care, most children go on to lead fully active, healthy lives.

It is important to take your child to pediatric specialists who are experts in treating only kids. At Children’s Orthopaedic and Scoliosis Surgery Associates, LLP our board certified, fellowship trained, specialists provide the best child-friendly care using the latest cutting-edge technology that results in the safest and most accurate outcomes. Please call our office at (727) 898-2663 to schedule an appointment.

Medically reviewed by Daniel C. Bland, MD Board Certified Orthopaedic Surgeon.

Children’s Orthopaedic and Scoliosis Surgery Associates LLP provides information and articles as a service to our readers. No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician. This blog provides general information and discussions about health and related subjects. The information and other content provided in this blog, or in any linked materials, are not intended and should not be construed as medical advice, nor is the information a substitute for professional medical expertise or treatment, If you have a medical concern, you should consult with your health care provider or seek other professional medical treatment. If you think you may have a medical emergency, call your doctor or emergency services immediately. The opinions and views expressed on this blog and website have no relation to those of any academic, hospital, health practice or other institution.

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