Why Does One Leg Feel Longer After a Hip Replacement?
A leg length discrepancy after hip replacement is one of the most common concerns following surgery. It can be a true difference, where the bone length has changed, or 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 takeaways
- 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 pelvic shift (apparent).
- Lying-down scans can miss the problem because gravity removes the load on your joints.
- A standing, full-length image of both legs and pelvis gives a clear, measurable picture.
- 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 frequently reported complaints after hip surgery. For some people it settles within months. For others it persists, causing a limp, back pain or frustration that nobody can give them a clear answer.
This page explains why it happens, the difference between a true and an apparent leg length change, and how standing imaging can give you a definitive measurement so you know exactly where you stand.
What is the difference between a true and apparent leg length discrepancy?
A true leg length discrepancy means the bones on one side are genuinely longer or shorter than 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 positions 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 and are sometimes made deliberately by the surgeon 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 disappear overnight.
This is why many people feel a difference even when X-rays show equal leg lengths. The measurement needs to account for the pelvis, not just the leg bones.
How do you know if your legs are different lengths after hip surgery?
You might notice one or more of the following signs in the weeks and months after your hip replacement. Some settle as you recover, but if they persist beyond three to six months they are worth investigating.
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 compensates 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 pinpoint why.
What causes a leg length difference after a hip replacement?
Several factors contribute, and it is often a combination rather than a single cause.
The position of the stem and cup in the new hip determines the effective length of that leg.
If the pelvis is tilted, one leg appears longer even though the bones are equal. This is common with uneven hips.
Muscles, tendons and the joint capsule tighten or stretch during surgery, altering how the leg sits.
You may have had unequal leg lengths before surgery without knowing, masked by joint wear and muscle adaptation.
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, those compensations do not reset instantly. This is why the problem is often felt at a distance 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 with a standing, full-length image that captures both legs and the pelvis in one shot, while you are weight-bearing.
Conventional X-rays taken lying down can be misleading. When you lie flat, gravity takes the load off your joints, your muscles relax, and 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 vanish completely on a lying-down film.
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, so measurements are precise and directly comparable side to side. It uses about 90% less radiation than a standard X-ray, around ten times less.
Want 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 assess 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 discrepancy is true, apparent, or a combination, and on how large it is. That is why accurate measurement comes first.
Common options that your surgeon or physiotherapist may consider include:
- Shoe raise or insole. A simple, non-invasive way to level out a small true difference.
- Targeted physiotherapy. Stretching and strengthening to address muscle tightness and pelvic tilt that create an apparent discrepancy.
- Gait retraining. Working with a physiotherapist to correct long-standing walking habits.
- Revision surgery. In rare cases where the discrepancy is large and causing significant problems, the implant position may need to be adjusted. This is a big decision and requires clear imaging evidence.
ScanAlign does not provide treatment. It provides the diagnostic imaging that gives you and your clinician a clear, measurable picture of what is happening, so any decision about next steps is based on evidence rather than guesswork. You can book an independent leg length measurement without a referral.
Frequently asked questions
Yes. A slight difference is very common and is sometimes intentional to improve joint stability. Most people adapt within a few months. If the feeling persists 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 persists beyond that point, a standing measurement can clarify whether it is true or apparent.
A shoe raise or insole can be very effective for a small true discrepancy. It will not help if the difference is apparent, caused by pelvic tilt or muscle tightness, because the bone lengths are already equal.
Lying-down X-rays remove the effect of gravity and muscle tension. Your pelvis may look level on a supine film 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, making one leg appear longer. This is a very common cause of apparent leg length discrepancy after hip replacement.
No. ScanAlign is a private, self-pay clinic. You can book directly without a GP or consultant referral.
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 relative to the pelvis, the opposite hip, and both legs, giving a clear picture of how the component sits when you are weight-bearing.
You can find up-to-date pricing information on the ScanAlign FAQs and cost page.
Clear, calibrated standing images with precise measurements are exactly the kind of evidence a revision surgeon needs. Having an independent imaging report can support a second opinion or surgical planning discussion.
Get a clear answer about your leg length
A free video consultation is the simplest way to find out whether standing imaging can help. 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.