How To Fix A Leg Length Discrepancy?

A leg length discrepancy is when one leg is measurably shorter than the other. Small differences of less than 2 cm are common and usually need no treatment. Larger differences, or ones causing pain and walking problems, may be treated with a shoe lift, physical therapy, or in some cases surgery.

Most people have some slight difference between their legs. For many, it is so small they never notice it. For others, the gap causes hip pain, lower back pain, or a limp that changes how they walk.

The right approach depends on how big the difference is, what is causing it, and whether it is causing symptoms. This article explains what the evidence shows about each option.

How Do You Know If You Have a Leg Length Discrepancy?

You may notice uneven wear on your shoes, a feeling that one leg is doing more work, or a limp that others point out. Some people see it in photos or notice one hip sits higher than the other.

But self-diagnosis is unreliable. What looks like a short leg is often something else. Pelvic tilt, muscle tightness, or a curved spine can make one leg appear shorter when the bones are actually the same length. This is called an apparent discrepancy.

A true discrepancy means the bones themselves differ in length. A functional discrepancy means the bones are equal but something in how you move or stand creates the appearance of a difference.

Only a clinician can tell the difference. A physical exam plus imaging can confirm whether the difference is real and how large it is.

What Causes One Leg to Be Shorter Than the Other?

Some people are born with it. Others develop it after an injury or during growth.

Common causes of a true discrepancy include:

• Congenital conditions present at birth, such as hip dysplasia
• Growth plate injuries in childhood that slow growth in one leg
• Bone infections or tumors affecting one leg
• Fractures that heal shorter than the original bone
• Conditions that affect bone development, such as a prior polio infection

Functional causes are different. They include muscle tightness, joint contracture, or pelvic misalignment. These do not involve a true difference in bone length, but they can make walking uneven and cause pain.

In adults, a discrepancy that was always there may only become noticeable when it starts causing symptoms. In children, a discrepancy can worsen during growth spurts if one growth plate is affected.

How Is Leg Length Discrepancy Measured?

Accurate measurement matters because treatment depends on the size of the difference.

A clinician may start with a physical exam. They place blocks of known height under the shorter leg until the pelvis levels out. This gives a rough estimate.

Imaging gives a more precise number. A standing X-ray of both legs, called a scanogram, measures each bone directly. This is the standard method for planning treatment.

Some clinicians use CT scans for even more precision, though this exposes the patient to more radiation. MRI can also be used but is less common for this purpose.

The size of the difference guides the treatment decision:

• Less than 2 cm: Usually no treatment needed unless symptoms are present
• 2 to 5 cm: Shoe lift or orthotic often recommended
• More than 5 cm: Surgical options may be considered, especially in children who are still growing

These thresholds are general guides. Individual decisions depend on symptoms, age, and overall health.

Can You Fix a Leg Length Discrepancy Without Surgery?

For most people, yes. Surgery is rarely the first option.

A shoe lift is the most common non-surgical treatment. It goes inside the shoe or is added to the sole. For small differences, an internal heel lift may be enough. For larger differences, the lift needs to be built into the sole of the shoe.

Lifts work best when the difference is between 2 and 5 cm. They can reduce limping, ease back and hip pain, and improve how you walk. Some people need a lift on the shorter side only. Others need adjustments to both shoes to keep the feet level.

Physical therapy can help with functional discrepancies. If muscle tightness or weakness is causing the unevenness, stretching and strengthening may correct it. This does not change bone length, but it can improve alignment and reduce pain.

For functional discrepancies caused by pelvic tilt or muscle imbalance, physical therapy is often the main treatment. A physical therapist can assess which muscles are tight or weak and design a program to address them.

Some clinicians also recommend orthotics for added support. These are custom shoe inserts that can help with alignment and comfort. Evidence for orthotics specifically in leg length discrepancy is limited, but they are widely used in clinical practice.

When Is Surgery Considered for Leg Length Discrepancy?

Surgery is usually reserved for larger differences, for children who are still growing, or for cases where non-surgical treatment has not helped.

The type of surgery depends on age and how much growth remains.

In children, a surgeon may stop growth in the longer leg. This is called epiphysiodesis. The goal is to let the shorter leg catch up during remaining growth. This works best when the child still has significant growth ahead.

In adults, or when growth is complete, surgery may involve shortening the longer leg or lengthening the shorter one. Bone lengthening is a complex procedure. It involves cutting the bone and gradually separating the ends so new bone fills the gap. This can take months and requires careful follow-up.

Surgery carries risks. These include infection, nerve damage, poor bone healing, and problems with the hardware used to hold the bone. Recovery can be long. For these reasons, surgery is generally considered only when the difference is large enough to cause significant problems and other options have not worked.

What Happens If You Do Nothing?

For small differences, doing nothing is often fine. Many people live their whole lives with a slight discrepancy and never have problems.

For larger differences, the body tries to compensate. This can lead to changes in how you walk, which over time may cause pain in the hips, knees, or lower back. The longer the discrepancy goes unaddressed, the more likely these changes become.

Some research suggests that discrepancies of more than 2 cm are more likely to cause low back pain. But the evidence is not definitive. Some people with larger differences have no pain, and some with smaller differences do.

If you have a discrepancy and it is not causing symptoms, regular check-ups may be all you need. If symptoms develop, treatment can be started then.

Can Leg Length Discrepancy Be Prevented?

True discrepancies caused by genetics or congenital conditions cannot be prevented. But some causes can be reduced.

Preventing injuries in childhood may help. Growth plate injuries are a common cause of discrepancy in children. Making sure children wear appropriate protective gear during sports and activities can reduce the risk of these injuries.

Prompt treatment of bone infections also matters. If an infection in a bone is not treated quickly, it can damage the growth plate and lead to a discrepancy later.

For functional discrepancies, staying active and maintaining good muscle balance may help. Regular stretching and strengthening can reduce the muscle tightness that sometimes causes the appearance of a short leg.