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Leg Length Difference
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Your right and left legs are rarely exactly the same length. A slight difference, usually under 1 cm, is almost universal. Possible signs include limping, tiptoe walking, or aches in the back, hip, knee or ankle. Differences above 2 cm are rare. Small differences often cause no trouble, and your podiatrist can measure the difference and suggest help, such as a shoe lift, if it does.
What is it?
Leg length difference means your right and left legs are not quite the same length. Almost everyone has a slight difference, usually less than 1 cm, so a small difference is normal.
There are two kinds. A structural difference means the leg bones really are different lengths. A functional difference means your legs look or feel unequal, but the bones are not shorter or longer. It can come from tight soft tissues (muscles and other soft parts), stiff joints, a tilted pelvis or spine, or the way your foot moves.
Most differences are under 10 mm. They often cause no symptoms, or your body easily makes up for them.
How big a difference has to be before it matters isn't agreed. This means a measurement alone doesn't decide what to do.
Who does it affect?
A leg length difference is common. Most people have one leg slightly longer than the other.
A bigger difference, of more than 2 cm, is uncommon: about 1 in 1000 people. A difference of 2 cm or more may cause problems, while smaller ones may not affect daily life.
In children, up to 90 per cent have some difference between their legs. A difference that really matters is rare.
A difference usually starts while a child is growing. An injury such as a broken bone, or a problem with the growth plates (the areas of growing cartilage near the ends of the long bones), may leave the legs unequal.
Signs and symptoms
Many people notice nothing at all. A difference often goes unnoticed until the way you walk changes or pain appears. This is also true in children.
When there are signs, they can include limping or walking on tiptoe, and pain in the back, hip, knee or ankle. Some people have one shoulder that sits higher. The knee on the shorter leg may bend back (hyperextend), while the knee on the longer leg stays bent.
Your body adjusts to the difference. For smaller differences, up to 22 mm, it often does this by tilting the pelvis. With larger differences, people start to bend the knee of the longer leg. Both legs can adjust, and more changes happen as the difference grows. Differences over 1 cm may change the way you walk.
A limp or leg pain in a child can have other causes. See the warning signs in the "When to see a podiatrist" section.
What causes it?
The cause depends on whether the difference is structural or functional.
A structural difference can be there from birth. Rare conditions can leave a leg bone very short or missing part of it. Or it can come later, from an injury, an infection, a tumour, radiation, paralysis or surgery. A past injury can leave one leg shorter. Removing an area of diseased bone can too.
A problem in the growth plate of one long bone can make that bone grow slowly, or not at all. If its pair keeps growing normally, the legs end up unequal. Growth plates sit at both ends of all the long bones, so this can happen in any of them.
A functional difference comes from outside the bones. Tight soft tissues, stiff joints, a tilted pelvis or spine, and the way your foot moves can all make one leg look or feel shorter.
How is it diagnosed?
Your podiatrist will watch you stand and walk, and check your posture, whether your pelvis tilts, and your knee position. They will note what they find.
Then they measure each leg with a tape from the front hip bone to the inside ankle bone, usually a few times, and take the average. A tape and standing blocks are useful screening tools, but less accurate than imaging.
Feeling your hip bones by hand is not reliable alone for telling which leg is shorter, or by how much.
A standing X-ray is the most accurate method but is seldom needed. It is chosen if the bones may also be bent.
Children are checked at routine visits. If a difference is growing or causing symptoms, see the "When to see a podiatrist" section.
Treatment
Treatment is a shared choice with your podiatrist, and it is always elective. The size of the difference alone doesn't decide it.
Looking after it at home
Wear supportive shoes with a lift.
Treatment from your podiatrist
Your podiatrist will measure the difference in millimetres and record how. For up to 2 cm, they may add a small lift inside your shoe, most often 0.5 cm to 1.5 cm thick. For 2 to 5 cm, a heel lift (a raise under the heel) worn in one shoe may ease some symptoms. Larger differences may need the shoe sole built up.
If you stand a lot at work, a difference should probably be corrected, with an orthotic (a shoe insert). They will start small and review your symptoms.
Lifts may help, though it isn't clear how well they work or what the best amount of correction is.
A child with a limp, or hip, thigh or knee pain, needs the cause checked before any lift. See the warning signs in the "When to see a podiatrist" section.
Other options
You may be referred to an orthopaedic specialist (a surgeon who treats bones and joints) if care hasn't helped, or the difference is large or growing. For a growing child, referral should come early, as the timing of surgery depends on remaining growth.
Surgery
Surgery is a choice, not something a number decides. A difference of more than 5 to 6 cm may need it.
Epiphysiodesis closes the growth plate of the longer leg to slow its growth. It has been used when the expected difference is 2 to 5 cm. Complications are common enough that the permanent operation in children needs careful discussion, and not every operation works as hoped. Staples have been linked with hardware failure and bent bones.
Limb lengthening is another option. Lengthening for looks is different from lengthening for a medical need. Surgery has real risks, so your surgeon should explain what it can achieve and what could go wrong. Less is known about how well these operations work in adults than in children and teenagers.
Recovery
Outlook depends on the size of the difference, its cause and your age. Most small differences stay harmless, but 2 cm or more is more likely to cause problems.
It is linked with low back pain, scoliosis (a sideways curve of the spine) and hip and knee arthritis. A link doesn't prove it caused them, so don't assume it explains new or worsening symptoms.
In children, small differences are usually harmless; a larger one may point to a cause. A growing child is monitored, and referred if the difference grows or causes symptoms.
It isn't clear whether lifts, inserts or exercise stop it coming back. How you feel and move matters more than the millimetre figure.
When to see a podiatrist
When to book
Book an appointment with your podiatrist if:
- your pain hasn't improved after a few weeks of home care
When to get help sooner
Get urgent medical assessment (see your GP today, or go to an urgent care clinic or the nearest emergency department) if:
- your child has a fever with a limp or a painful, red, hot or swollen joint, or seems very unwell with foot or leg pain: go straight away, without waiting for an appointment
- your child suddenly has severe pain in one joint and is limping
See your GP soon if:
- you have lost weight without trying
- you have pain at night or at rest that doesn't settle
- your child has a limp that hasn't improved after a week, limps without pain, or doesn't want to put weight on their foot
See your podiatrist or GP soon if:
- your child walks on tiptoe and also can't stand with heels down, has one side different from the other, has very bulky calves, or seems unusually stiff or unsteady
Frequently asked questions
Why do I feel uneven after a hip replacement?
Your legs may feel unequal even when the bones haven't changed. Tight muscles around the hip after surgery, or a tilted pelvis, can create that feeling. Many people notice a difference of more than 10 mm.
How accurate is measuring leg length with a tape?
A tape measure may reach a precision of up to 5 mm and can be comparable to a CT scan (a detailed body scan), though it is generally less accurate than imaging and is best used as a screening tool. Taking the average of two or three measurements helps. Measuring with blocks depends a lot on the skill of the person doing it.
Why can't anyone tell me why I have it?
In about 95 per cent of structural differences, the reason isn't known. Most small differences have no clear cause. It isn't due to anything you did, so there is nothing to blame yourself for.
Could a leg length difference be a reason my back or hip hurts?
It may be, but it may not. Pain in the back, hip or knee has many causes, and having a difference doesn't prove it is the one. Your podiatrist can look at the whole picture, including how you stand and walk.