Leg length difference: when does it matter
Many people have a leg length difference. If we were to measure everyone, we know that more than 90% of all people have a leg length difference. The average difference is about 0.5 cm. In about 20% of the population, there is more than 1 cm of leg length difference. And 1 in 1,000 has a leg length difference of more than 2 cm. The exact difference must be measured by an X-ray looking at the difference in height of both hips. This is rare and is a relatively expensive examination. In practice, we often see measurements taken from recognizable anatomical points in our body from the hip to the foot. This method is far from perfect but gives an indication of a possible leg length difference. But the most important question is: how important is a leg length difference in relation to pain symptoms.
More than 90% of the population has a leg length difference
Possible cause of pain
When a physical therapist or doctor discovers a leg-length difference, it is easy to point to it as the cause of pain. But can we say this so directly? Several studies have been conducted on the relationship between leg length difference and pain. A study where they found people with a leg length difference and MET BACKGROUND compared with people with a leg length difference WITHOUT BACK pain showed the following. The average leg length difference in the group with pain was 5.1 mm and the average difference in those without pain complaints was 5.2 mm. This small difference shows that the measured leg length difference does not particularly contribute to pain symptoms. In fact, the average leg length difference of those without pain complaints is somewhat larger.
Another group where a leg length difference is often measured is people with a hip prosthesis or after a hip bone fracture. Both can result in a leg length difference. Although there is an average difference of about 3 inches after surgery or fracture, we do not see these people develop more or less back pain. Nor do we see any long-term change:
- development of hip osteoarthritis
- loss of function
- comfort
- satisfaction after surgery
So does it really matter? Should we put so much effort into fixing this?
When does it matter?
To answer this question, we need to look at 2 different factors:
- The actual difference in length
- The individual load level
A leg length difference under 1 cm is most likely not a cause of complaints elsewhere in the body. A greater difference than 1 cm seems more relevant, especially in combination with a high physical load. When there is no higher physical load, we see that makes little difference.
This means, then, that in people with leg lengths greater than 1 cm and a low daily physical load such as cycling or an office job, it is unlikely that the leg length difference is the reason for the symptoms.
What can we do about it?
When it does, an insole may be helpful in reducing symptoms. The height of the insole and the type will vary from person to person. What is even more important than an insole is to look carefully at other factors such as physical activity, sleep and the taxability. All of these can help reduce symptoms and promote recovery.
A leg length difference is normal up to a certain limit. When you are first told that there is a leg length difference it can be quite a shock. It is often thought that it MUST be fixed. So understand that in most cases this is not necessary and that a small leg length difference is not immediately the reason for possible complaints. Nor is it that you may develop complaints more quickly in the future. No back problems, no osteoarthritis, this does not have to be the case. We are far from being symmetrical. The evidence between abnormalities in stance and pain is very minimal or often nonexistent. Focus less on the leg length difference and more on what you can influence!
