Yes. Limb lengthening surgery can correct an unequal leg length by gradually increasing the length of the shorter limb until the difference is reduced or, in selected cases, nearly eliminated.
The procedure uses a process called distraction osteogenesis. A controlled cut is made in the shorter bone, and the two bone segments are gradually separated. As they slowly move apart, the body forms new bone in the gap.
However, having unequal leg length does not automatically mean that limb lengthening surgery is necessary. Small differences may cause little or no functional difficulty and can sometimes be managed with a shoe lift or other conservative measures. In children who are still growing, procedures that slow the growth of the longer leg may also be considered.
Understanding the size and cause of the discrepancy is therefore the first step in deciding whether lengthening is appropriate. You can learn more about the procedure on the Limb Lengthening Surgery page.
What Is an Unequal Leg Length?
Unequal leg length, medically known as leg length discrepancy (LLD), means that one lower limb is shorter than the other. The difference may involve the femur, tibia, or both bones. It can develop for many reasons, including:
- Congenital differences present from birth
- Previous fractures or other injuries
- Growth plate damage
- Bone infections
- Developmental conditions
- Previous orthopedic surgery
- Bone or joint conditions affecting growth
- Other conditions that cause one limb to grow differently from the other
The discrepancy may remain stable, or it may increase while a child is still growing. This distinction is important when planning treatment.
How Does Limb Lengthening Correct the Difference?
The basic idea is straightforward: instead of shortening the longer leg, the surgeon gradually adds length to the shorter one. The process generally involves four stages:
- Assessment and planning: The exact difference and location of the shortening are measured using clinical examination and imaging.
- Controlled bone cut: The shortened bone is surgically divided.
- Gradual distraction: A lengthening device slowly separates the bone segments.
- New bone formation: Bone develops in the gap and gradually becomes stronger.
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
The process takes place over weeks or months rather than during a single operation. The gradual approach gives the new bone time to form while allowing the surrounding soft tissues to adapt.
How Much Leg Length Can Be Corrected?
There is no single amount of discrepancy for which limb lengthening is automatically recommended. Historically, treatment decisions have often been guided by the size of the discrepancy. A commonly used approach is to consider conservative correction for smaller differences, growth-modifying procedures in selected growing children, and lengthening or shortening procedures for larger discrepancies.
However, current literature emphasises that the size of the discrepancy is only one part of the decision. Symptoms, functional limitations, age, cause of the discrepancy, bone condition, predicted growth and the patient's overall circumstances also matter.
For larger discrepancies, particularly those that cannot be comfortably managed with external aids, limb reconstruction and lengthening may become an important treatment option.
Does Every Unequal Leg Need to Be Made Exactly the Same Length?
No. Complete equalisation is not always necessary or appropriate. Some people have a small difference without significant symptoms, while others may function well with a modest residual discrepancy after treatment.
Trying to achieve exact equality can also expose the patient to additional surgical or mechanical demands. The treatment goal is therefore usually based on improving limb balance and function rather than simply reaching an identical measurement at all costs. In some treatment plans, a small residual difference may be intentionally accepted.
What If the Difference Is Small?
Small leg length differences may not require surgery. Depending on the size of the discrepancy and whether it causes symptoms, options may include:
- No treatment when the difference is clinically insignificant
- A shoe insert or lift
- A modified shoe
- Physical therapy when movement or muscle imbalance contributes to symptoms
- Monitoring, particularly in growing children
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
A review of leg length discrepancy treatment notes that conservative measures are commonly considered for moderate discrepancies and that full equalisation is not always required.
What If the Person Is Still Growing?
The approach can be different in children and adolescents because the longer leg may still have growth remaining. Instead of lengthening the shorter leg, surgeons may sometimes slow or stop growth in the longer leg so that the shorter leg can gradually catch up.
This is called epiphysiodesis and involves treating a growth plate to reduce or stop further growth at a carefully calculated time.
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
It is not suitable for every child. The decision depends on the predicted final discrepancy, skeletal maturity, remaining growth and the underlying cause of the difference.
What About Adults With Unequal Leg Length?
Once skeletal growth is complete, growth-modification procedures are no longer an option. Treatment therefore focuses on correcting or accommodating the existing difference. Depending on the size and location of the discrepancy, possible approaches include:
- Shoe modification or lift
- Orthotic management
- Shortening of the longer limb in selected cases
- Lengthening of the shorter limb
Limb lengthening may be considered when increasing the shorter limb is preferable to shortening the longer one and when the patient is an appropriate candidate for the procedure.
When Is Limb Lengthening Considered Instead of Shortening?
Both lengthening and shortening can potentially reduce a leg length difference, but they work in opposite ways.
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
| Limb lengthening | Limb shortening |
|---|---|
| Increases the length of the shorter limb | Reduces the length of the longer limb |
| Requires gradual bone distraction and new bone formation | Removes or shortens a section of bone |
| Can preserve the patient's overall height | Results in some reduction in overall height |
| Usually involves a prolonged lengthening and consolidation process | May involve a shorter biological process, depending on the procedure |
The choice depends on the amount of discrepancy, the patient's age, bone anatomy, overall limb proportions, functional requirements and the risks associated with each option.
How Is the Exact Leg Length Difference Measured?
Accurate measurement is essential because treatment decisions should not be based simply on how uneven the legs appear. The assessment may include:
- Physical examination while standing
- Measurement using blocks or other clinical methods
- Standing X-rays
- Long-leg radiographs or other specialised imaging
- Assessment of the femur and tibia separately
- Evaluation of the pelvis, hips, knees and ankles
Can Limb Lengthening Correct the Entire Difference?
In many cases, substantial correction is possible, but complete correction cannot be guaranteed. The amount that can safely be lengthened depends on the original bone length, bone quality, surrounding soft-tissue flexibility, joint condition and the patient's response during treatment.
Very large discrepancies may require staged treatment rather than attempting to correct the entire difference in one lengthening procedure. The objective is to achieve the necessary correction while allowing the bone and surrounding tissues to adapt safely.
What Happens During the Lengthening Process?
After the bone has been divided and the lengthening device positioned, there is usually an initial healing period before distraction begins.
The bone is then gradually lengthened, often at a rate close to 1 mm per day, although the rate is adjusted according to the patient's clinical and radiographic response.
As the gap widens, new bone forms between the segments. At the same time, the muscles, tendons, nerves and other soft tissues gradually adapt.
Once the desired correction has been reached, the new bone enters the consolidation phase. During this period, it becomes progressively stronger before normal activity can be fully resumed.
What If the Leg Length Difference Is Causing Symptoms?
Not every symptom associated with unequal leg length is necessarily caused by the discrepancy itself. The relationship between leg length difference and problems such as back pain, gait changes and joint degeneration remains an area where the evidence is not completely consistent.
Some people with a measurable difference have no symptoms, while others may experience changes in walking mechanics or discomfort. For this reason, doctors generally consider both the measured discrepancy and the patient's actual functional problems when deciding whether treatment is warranted.
How Long Does It Take to Correct Unequal Leg Length?
Correction takes time because the bone cannot safely be lengthened by several centimetres at once. The distraction phase generally occurs over several weeks, followed by a longer period during which the new bone consolidates and becomes stronger.
The overall duration depends on the amount of lengthening required and how quickly the bone forms and matures. Physical therapy and regular imaging are usually needed throughout the process.
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
Can Limb Lengthening Be Used for Very Large Leg Length Differences?
Yes, limb lengthening can play an important role in managing substantial discrepancies, but very large differences can require more complex treatment.
Depending on the cause and the amount of shortening, treatment may involve staged lengthening procedures, lengthening at more than one bone segment, or a combination of techniques.
Attempting to correct a very large discrepancy in one stage may place excessive stress on the bone and surrounding soft tissues. A staged approach can sometimes make the overall reconstruction more manageable.
The Bottom Line
Limb lengthening surgery can correct unequal leg length by gradually increasing the length of the shorter limb. The process relies on distraction osteogenesis, allowing new bone to form while the surrounding tissues gradually adapt.
However, surgery is not automatically required simply because one leg is shorter. The size of the discrepancy, its cause, the patient's age and skeletal maturity, symptoms, bone and joint condition, and available alternatives all influence the treatment decision.
For children who are still growing, growth modification may sometimes correct the difference without lengthening the shorter limb. For adults and for larger discrepancies, limb lengthening may be considered when other approaches are unsuitable or insufficient.
The most appropriate treatment is therefore the one that addresses the discrepancy while preserving long-term limb function, rather than simply aiming for an identical measurement between the two legs.
