Leg length discrepancy [Best Treatment, Exercises, Shoes & Heel Lifts]

What is Leg Length Discrepancy & Causes:

Leg length discrepancy is also known as Anisomelia. It is a condition where there is noticeably an unequal length between the 2 lower extremity limbs. It can be classified into 2 categories; anatomical and functional.

In anatomical type, there is a structural inequality in limb length. This may be due to a congenital abnormality at birth, such as scoliosis or acquired conditions like fractures, trauma (injury), bone infections, bone cancers, surgical problems like following joint replacement, and certain orthopedic degenerative disorders. In anatomical type, there is a true difference in your bone length.

In functional limb length discrepancy, the asymmetry is not structural, and there is no shortening of bones of your lower limbs. It is due to alteration of the lower limb mechanics. Ex: Muscle weaknesses, ligament shortening or laxity, joint contractures, mal-alignments, abnormal knees, hips, feet, and ankles. Radiography does not help to diagnose these faulty mechanics. Leg length discrepancy may become problematic to active, involved in sports, and those on their feet most of the day.

This is the major cause of leg length discrepancy & is important for how to treat leg length discrepancy.

How common is limb length discrepancy?

Around 90% of the population has some degree of leg length discrepancy.

• Usually, many are asymptomatic who have a mild degree of discrepancy.
• The average discrepancy is around 5mm.
• However, if the discrepancy is more than half an inch, it is considered clinically significant.
• It is quite a common condition, although we may not be fully aware of it.
• Research by radiographic measurements has found that 70- 90% of the normal population had some discrepancy in their bone leg length.
• Out of which 20% showed a difference of more than 9mm.

What is an acceptable leg length discrepancy?

• You may wonder how much leg length discrepancy is normal. A difference of 10 – 20mm is considered normal or insignificant by many clinicians.
• Limb length discrepancy up to 20mm can be passively compensatory.
• But if it is more than 20mm, active muscular compensatory measures are needed.

Leg length discrepancy symptoms:

Functional leg length discrepancy symptoms can be:

• Lower back pain.
• Hip pain.
• Hamstring pain.
• Knee pain. 
• Calf & ankle pain:
• Plantar fasciitis.
• Ball of the foot pain.
• Heel pain.
• Muscle imbalances & joint pain.
• Difficulty walking.
• Difficulty standing for long periods of time.

Is leg length discrepancy a disability?

Usually, if the leg length discrepancy is 5mm or less, it is not significant, especially in the absence of pain and dysfunction. Leg length discrepancy becomes a disability when severe indifference or the symptoms that the patient experience interferes with their day-to-day routine and lifestyle. Disability is usually associated with the long leg. When there is a compensatory mechanism for the discrepancy, such as scoliosis or pelvic tilt, these also can associate with the disability.

Inequality of the limb length can be divided into 3 categories;

• Mild – when the leg length discrepancy is from 0- 30mm
• Moderate – When the discrepancy is between 30 – 60mm
• Severe – if the discrepancy of leg length is more than 60 mm

Intervention is needed if the patient is symptomatic and depending on the magnitude of the discrepancy.

Who to see for leg length discrepancy?

• You should see a pediatric podiatrist or a pediatric orthopedic surgeon if you have any doubts regarding any discrepancy between your or your child’s leg length.
• A podiatrist can help evaluate and treat your functional leg length discrepancy through heel lifts, custom orthotics, insoles, and shoe lifts.
• After taking a complete medical history and physical examination, your doctor will calculate the difference in leg length.
• Investigations like X-rays or CT scans will be ordered to confirm.
• In functional type, although there is an apparent difference, the measured length will not differ.

How to diagnose Leg length discrepancy?

Radiography helps to identify a lower limb discrepancy accurately. Usually, X-Rays are adequate, but CT scans may be used to identify any contractures of knees and hips.

What is a scanogram for leg length discrepancy?

This is a method for measuring discrepancy in leg length by using digitized radiographs by a CT scanner. It is a rapid method that delivers 50 – 100 times less radiation than the conventional radiographic method.

How to measure leg length discrepancy?

How to perform a leg length discrepancy measurement:

Manual tape measurements are taken between 2 points while the patient lays supine. Commonly defined points are between your anterior iliac spine and the medial malleolus, the anterior inferior iliac spine, and the lateral malleolus. It is a direct method but may not be exactly accurate.

In an indirect method, your doctor can palpate bony landmarks while you are standing. For example, your iliac spines or crests are palpated together and see whether both are at the same horizontal level or whether there is an angle that means there is a leg length discrepancy.

By using PALM or the Palpation meter:

It is a valid and reliable instrument to measure any difference in your pelvic height. PALM is cost-effective and convenient.

Your clinician may also use blocks to measure the limb lengths, although accurate measurements depend on the clinician.

Leg length discrepancy test:

The best leg length discrepancy test is to get seen by your podiatrist, biomechanical specialist, or a physical medicine and rehab specialist for a biomechanical evaluation. We specialize in gait analysis (walking analysis) to assess for functional limb length discrepancy.

It is rare that a bone measurement with yields useful information. We find that most unequal leg length is due to muscle, tendon, or soft tissue causes.

This means that it manifests and shows itself during walking and running. Thus it is not as simple as just getting a shoe lift, shoe insert lift, or a heel lift to fix the problem. The true solution is to identify why there is an imbalance and correct the soft tissue problem.