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Leg Length Difference

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Up to 90% of Australians have some discrepancy in the length of their legs when measured anatomically. While smaller leg length differences (LLDs) do not produce any noticeable differences, more notable LLDs can lead to changes in a person’s gait that can have painful and damaging consequences.

What Is A Leg Length Difference?

A leg length difference, also known as a limb length discrepancy, is a physical difference in the length of their legs when two anatomical points are measured. While it’s not surprising given that our bodies are not perfectly symmetrical, this asymmetry can be significant because it has the potential to cause pain and other problems, interfering with a person’s movement and their quality of life. When evaluating a leg length difference, there are two key types: 

• Structural leg length difference: this is measured when a person is non-weight bearing (such as lying down) and your podiatrist identifies two anatomical points, such as your lateral malleolus (the bump on the outside of your ankle) and your iliac crest (the bony protruding bump on your hip bone). Both sides are measured and a difference in measurement values means that there is a difference in the length of your femur or tibia. This difference may be a result of an injury, disease, a byproduct of surgery or may be a natural length variation that leaves one leg shorter than the other.
  
• Functional leg length difference: a functional difference is measured when a person is standing - and when their feet and legs are functional. People with a functional LLD may have the same structural leg length when anatomical measurements are taken, but due to the way the muscles, bones, connective tissues and joints work together when standing or walking, a leg length difference is created. We often see functional differences linked to tight, contracted muscles, such as at the hips. We also see it when ligament laxity or tendon dysfunction affects one foot more than the other. Neurological diseases are another common cause for functional differences. A common example is when posterior tibial tendon dysfunction causes one foot to become flatter than the opposite foot. The hip and knee of the flatter foot are more likely to be sitting lower to the ground than that of the other leg, creating a leg length difference.
  

What Length Difference Causes Problems?

Studies looking at leg length differences have found that up to 90% of people have differences with an average 5.2mm - just half a centimetre. Specifically, a recent systematic review on the value of structural (anatomical) leg length differences in the population showed:

• 41.3% had a difference of between 0-4mm
  
• 37.4% had a difference of between 5-9mm
  
• 15% had a difference of between 10-14mm
  
• 6.4% had a difference of over 14mm
  

Statistically speaking, leg length differences of more than 5 mm are related to an increased risk of osteoarthritis of the hip and knee joints as well as low back pain and lumbar scoliosis, a curvature of the lumbar spine. With this said, it’s important to note that each person can compensate for their LLD in different ways, which means that some people with a 10mm LLD (for example) will be asymptomatic, while others may present with symptoms

What Causes A Leg Length Difference?

While some leg length differences may be natural, there are various other potential causes of a leg length difference, such as:

 

• Developmental abnormalities
  
• Bone injuries which heal in a shortened position
  
• Injury to the growth plate in a bone during childhood
  
• Bone disease and infection
  
• Neurological conditions
  
• Inflammatory conditions affecting the joints
  
• Abnormal foot biomechanics
  
• Contractures of joints or connective tissues
  
• Ligament laxity
  
• Natural differences present from birth
  

Signs And Symptoms

Having a leg length difference creates a tilt at the hips and various joints in the feet and legs, and can adversely affect your spine too. It can result in other joints and structures being overloaded, stressed, stretched and restricted in their function. This can present in a variety of symptoms, from a limping gait to shorter steps and walking speed, to overuse injuries, stress fractures - and hip, knee and back pain. Here at The Feet People, we look for:

• Greater loading on one foot when completing our pressure analysis testing
  
• Markedly different wear patterns between your shoes
  
• Hip hitching or a exaggerated bending of the knee when completing your gait analysis
  
• Recurrent tendinopathies (often in multiple areas)
  
• Foot or leg fatigue, or joint aches
  
• Uneven steps - shorter steps on the side with the shorter leg
  
• Pain in the hips, knees or back
  
• Stress fractures or other problems that don’t appear to have a traditional cause
  

The Impact Of A Leg Length Difference

To better understand the true impact of a leg length difference on your body and why the above symptoms may occur, imagine standing with one leg that is slightly longer and one that is slightly shorter. Your shorter leg will have less contact with the ground in the heel region, and your body will likely try to compensate and help bring the shorter foot closer to the ground by tilting your hip down on the shorter side, or keeping your longer knee bent. 

When walking and pushing off from the shorter leg, your longer leg may hit the ground instead of swinging through because of its length, so your body will compensate by hitching the hip up, having you swing your leg outwards away from your body instead of straight forwards, or having you lift your knee. These are some of many compensations and all add up when it comes to the potential stress and strain on your joints and body. Other compensations and the symptoms they may cause include:

• Foot: the foot on the longer side may pronate to bring it closer to the ground and functionally shorten it, while the shorter foot tends to hold a higher arch.
  
• Knee: the knee on the long leg side may flex easily or hyperextend as a compensation for LLD
  
• Ankle: the ankle on the shorter leg tends to angle downwards (plantarflex) early to make ground contact, which when chronically repeated can lead to weakness of a muscle called the tibial anterior, making it more difficult to point the toes upwards.
  
• Hips: studies show that there can be greater forces through the acetabulum (the socket of the hip bone in which the head of the femur sits) of the side with the longer leg. This is due to compensation such as external rotation of the leg which can uncover the head of the femur and lead to a more concentrated area of force or pressure
  
• Pelvis: like in the example above, pelvic obliquity (a tilting of the pelvis up toward the long side limb and down toward the short side limb) is a common compensation for a leg length difference 
  
• Back: due to the effects of various compensations in the hips and lower limbs, research finds that having a leg length difference of over 15mm makes you over five times more likely to develop chronic back pain. In those with standing occupations, this reduced down to just 6mm.
  

Treating A Leg Length Difference

To manage a leg length difference, we must first understand the size of the difference, the effects that it is currently having on your gait, joints and muscles, and how your body may be compensating. This is done through a comprehensive assessment with our podiatrists at our Brisbane CBD or Newmarket clinics. While we use manual tools to measure both structure and functional LLDs, we can also refer you to have your structural difference formally measured with a CT scan.

From here, your podiatrist wall design a unique management plan based on your symptoms that may include:

• Custom foot orthotics (or heel lifts) to help support your foot biomechanics while restoring better symmetry and alignment through the height raise in the orthotics.
  
• Footwear modifications such as a full length raise to help bring your lower limbs into better alignment and therefore reduce stress on your joints, muscles, and tissues 
  
• Addressing muscle contractures using techniques like a myofascial release, dry needling, foot mobilisation, stretching programs and more
  
• Strengthening weakened muscles that may have occurred as a result of the compensations for your leg length difference
  
• Footwear recommendations to help support you in balancing your leg length difference
  
• Managing skin problems like corns and calluses that may arise, particularly if one leg is bearing significantly more weight