Why Does One Leg Feel Longer After a Hip Replacement?
A leg length difference after hip replacement is one of the most common worries after surgery. It can be a true difference, where the bone length has changed. Or it can be an apparent difference, where tightness, pelvic tilt or swelling make one leg feel longer even when it is not. Standing, weight-bearing imaging is the most reliable way to measure the difference accurately.
Key points
- Feeling that one leg is longer than the other is very common after a hip replacement.
- The difference can be real (true) or caused by muscle tightness, swelling or a shift in the pelvis (apparent).
- Scans taken lying down can miss the problem because gravity takes the load off your joints.
- A standing, full-length image of both legs and the pelvis gives a clear picture that can be measured.
- Knowing the exact type and size of the difference guides the right next step.
If you have had a total hip replacement and something feels off when you walk, you are not imagining it. A noticeable leg length discrepancy is one of the most often reported complaints after hip surgery. For some people it settles within months. For others it stays. It can cause a limp, back pain, or the frustration of nobody giving a clear answer.
This page explains why it happens and the difference between a true and an apparent change in leg length. It also explains how standing imaging can give you a definite measurement, so you know exactly where you stand.
What is the difference between a true and an apparent leg length discrepancy?
A true leg length discrepancy means the bones on one side are really longer or shorter than on the other. An apparent discrepancy means the bones are the same length, but something else makes one leg seem longer.
A true difference is structural. During a hip replacement, the surgeon places the new implant to restore the hip's centre of rotation, offset and stability. Sometimes the implant sits slightly higher or lower than the natural joint did. The result is a measurable change in the length of the leg from hip to ankle.
Small true differences are very common. Sometimes the surgeon makes them on purpose to improve joint stability. Larger differences may cause a noticeable limp or discomfort.
An apparent difference is not about bone length. It is caused by things like muscle tightness, pelvic obliquity (where the pelvis tilts to one side), swelling, or changes in posture after surgery. Your body may have adapted to years of hip arthritis by tilting the pelvis or tightening certain muscles. After the joint is replaced, those habits do not go away overnight.
This is why many people feel a difference even when X-rays show equal leg lengths. The measurement needs to take the pelvis into account, not just the leg bones.
How do you know if your legs are different lengths after hip surgery?
You may notice one or more of these signs in the weeks and months after your hip replacement. Some settle as you recover. If they last beyond three to six months, they are worth looking into.
Walking feels uneven, as if one foot hits the ground before the other.
Clothes or shoes wearing unevenly on one side is a practical clue.
The body makes up for unequal legs by shifting the spine or loading the opposite knee.
Many people simply sense that the operated side is too long or too short, even if they cannot say exactly why.
What causes a leg length difference after a hip replacement?
Several factors play a part. It is often a mix rather than a single cause.
The position of the stem and cup in the new hip decides the effective length of that leg.
If the pelvis is tilted, one leg looks longer even though the bones are equal. This is common with uneven hips.
Muscles, tendons and the joint capsule tighten or stretch during surgery. This changes how the leg sits.
You may have had unequal leg lengths before surgery without knowing. Joint wear and muscle adaptation can hide it.
Your body is a connected chain from feet to head. Years of hip arthritis often cause the pelvis to shift, the spine to curve, and the opposite knee or ankle to take extra load. After surgery restores the hip, these adjustments do not reset straight away. This is why the problem is often felt away from the hip itself.
How is leg length measured accurately after hip surgery?
The most reliable way to measure leg length after a hip replacement is a standing, full-length image. It captures both legs and the pelvis in one shot while you are weight-bearing.
Ordinary X-rays taken lying down can be misleading. When you lie flat, gravity takes the load off your joints and your muscles relax. Your pelvis may flatten into a position it never holds in real life. A small tilt that causes a noticeable limp when you walk can disappear completely on a lying-down X-ray.
EOS scanning for leg length discrepancy solves this by imaging you standing up, exactly as your body works day to day. ScanAlign standing imaging captures both legs from hip to ankle on a single, calibrated image. This means measurements are precise and can be compared directly side to side. It uses about 90% less radiation than a standard X-ray, around ten times less.
Would you like an independent, standing measurement of your leg lengths after hip surgery?
Book a free video consultationA note on MRI. EOS shows bones, joints and alignment. If your surgeon needs to check soft tissue around the implant, the joint capsule, or nearby nerves, MRI is usually the better tool. The two scans answer different questions, and sometimes both are needed.
What can be done about a leg length difference after hip replacement?
The right approach depends entirely on whether the difference is true, apparent, or a mix, and on how large it is. That is why accurate measurement comes first.
Common options your surgeon or physiotherapist may consider include:
- Shoe raise or insole. A simple, non-invasive way to even out a small true difference.
- Targeted physiotherapy. Stretching and strengthening to address muscle tightness and pelvic tilt that create an apparent difference.
- Gait retraining. Working with a physiotherapist to correct long-standing walking habits.
- Revision surgery. In rare cases where the difference is large and causing significant problems, the implant position may need to be adjusted. This is a big decision and needs clear imaging evidence.
ScanAlign does not provide treatment. It provides the diagnostic imaging that gives you and your treating clinician a clear, measurable picture of what is happening. This way, any decision about next steps is based on evidence rather than guesswork. You can book an independent leg length measurement without a referral.
Before you start a treatment, or change the one you are on, it is worth getting a detailed diagnosis. Knowing whether the cause sits in the pelvis, the legs or the spine changes what will actually help.
Frequently asked questions
Yes. A slight difference is very common and is sometimes made on purpose to improve joint stability. Most people adapt within a few months. If the feeling lasts or affects your walking, it is worth getting a proper measurement.
Most surgeons suggest waiting at least three months to let swelling settle and muscles recover. If a noticeable difference lasts beyond that, a standing measurement can show whether it is true or apparent.
A shoe raise or insole can be very effective for a small true difference. It will not help if the difference is apparent, caused by pelvic tilt or muscle tightness, because the bone lengths are already equal.
X-rays taken lying down remove the effect of gravity and muscle tension. Your pelvis may look level on a lying-down X-ray but tilt when you stand. A standing, weight-bearing image captures what your body actually does under load.
Pelvic obliquity means the pelvis is tilted to one side. Even if both legs are structurally the same length, the tilt raises one hip and lowers the other. This makes one leg look longer. It is a very common cause of apparent leg length difference after hip replacement.
No. ScanAlign is a private, self-pay clinic. You can book directly, without a referral from your doctor or a consultant.
An EOS scan uses about 90% less radiation than a standard X-ray, around ten times less. This makes it a very low-dose option for full-length leg imaging.
Yes. A standing full-length image shows the implant's position compared with the pelvis, the opposite hip and both legs. It gives a clear picture of how the implant sits when you are weight-bearing.
The price for patients travelling from abroad is confirmed during the free video consultation. You can read more on the ScanAlign FAQs and cost page.
Clear, calibrated standing images with precise measurements are exactly the kind of evidence a revision surgeon needs. An independent imaging report can support a second opinion or a discussion about surgical planning.
Get a clear answer about your leg length
A free video consultation is the simplest way to find out whether standing imaging can help you before you plan a trip to London. No referral needed.
Book a free video consultationWritten by Abbas Dhami (Specialist Diagnostic Radiographer)
Sources
- Konyves, A. and Bannister, G.C., "The importance of leg length discrepancy after total hip arthroplasty," The Journal of Bone and Joint Surgery (British), 2005; 87-B(2): 155-157.
- Meermans, G. et al., "Measuring leg length discrepancy: is the EOS imaging system a valid alternative to full-length radiographs?," Orthopaedics & Traumatology: Surgery & Research, 2020.
- NHS, "Hip replacement: Recovery," nhs.uk.
This page is general information and not a diagnosis.
ScanAlign is the trading name of CoreMed Solutions Ltd and operates under The Harley Street Hospital's CQC licence.