Leg Length Difference After Hip Replacement: Why One Leg Feels Longer

Feeling that your operated leg is longer is one of the most common surprises after a hip replacement, and in most people the legs turn out to be equal or very nearly so; the feeling comes from a tilted pelvis and tight muscles that take weeks to months to catch up with the new joint. I was certain, the first week home, that my surgeon had left my right leg too long. I stood in front of the wardrobe mirror, compared the hems of my trousers, and drafted a worried question for my six-week check. By the time the appointment came round, I could not feel any difference at all. Here is why that happens, how to tell the common kind from the less common kind, and what helps, with the medical side checked by Ms Raman.

How common it is

Perceiving a leg length difference is common, and a real, measurable one is much less so. A study of people several years after hip replacement found that about 30% felt their legs were different lengths. When the researchers checked X-rays, only about a third of those who felt a difference actually had a measurable one, and some people with a measurable difference had never noticed it ¹.

The same study found that people who perceived a difference reported worse scores on a standard hip questionnaire, and about a third of them used a shoe raise ¹. So the feeling matters, even when the X-ray is reassuring. It deserves to be taken seriously rather than waved away, but it is worth knowing going in that the feeling and the measurement often disagree.

Why the new leg feels long

The commonest reason is that your body is still arranged around the old, worn hip. Osteoarthritis tends to wear the joint down slightly, and over years of pain most of us learn to stand and walk in a way that protects it. The pelvis tilts, some muscles shorten and tighten, and the brain’s sense of where the leg is (proprioception) recalibrates around all of that. The study above suggests that pelvic tilt and altered proprioception around the hip may explain why perception runs ahead of reality ¹.

When the joint is replaced, the leg is restored to something close to its proper length, but the tilted pelvis and tight muscles are still there. The result is a leg that feels too long. This is often called an apparent or functional difference, as opposed to a true difference in the bones and implant. In a series of 100 people followed after hip replacement, 14% had this kind of functional difference with a tilted pelvis about a month after surgery, and in every one of them the symptoms had resolved by six months ².

That matched my experience exactly. My pelvis had spent two years hitched up on one side, and it took a few weeks of walking, stretching, and the exercises in my hip replacement exercise guide before it levelled out. The same mechanism sits behind a lot of early limping, which I wrote about in limping after a hip replacement.

When the difference is real

A small true difference is sometimes the price of a stable hip. Surgeons aim to make the legs even, but the American Academy of Orthopaedic Surgeons notes that a surgeon may lengthen or shorten the leg slightly to maximise the stability and mechanics of the new joint ³. The tension in the soft tissues around the hip is part of what keeps the ball in its socket, and a joint that is too loose is more prone to dislocation. When a real difference does occur, it is most often the operated leg that ends up slightly longer ¹.

Ms Raman put it to me this way when I asked about it for this article: surgeons plan leg length carefully before the operation using X-ray templates, check it during surgery, and still have to make a judgement in theatre between perfect symmetry and a stable hip. A few millimetres one way or the other is often unnoticeable; a larger difference is uncommon. Asking how your surgeon plans for leg length is one of the questions I would add to the list to ask your hip surgeon.

How to tell which kind you have

Only a proper measurement can tell an apparent difference from a true one, so do not try to settle it with a mirror or a tape measure at home. A clinician can examine you lying down and standing, and an X-ray of the pelvis lets them compare fixed bony landmarks on each side. That separates a difference in the leg itself from one created by the pelvis, the spine, or tight muscles.

A few patterns are worth noting before your appointment, because they help the conversation:

• When you notice it. An apparent difference often feels worse when you are tired, after sitting, or first thing in the morning.
• Whether it is changing. A difference that is fading week by week is behaving like the functional kind.
• What it does to your walk. A dip on one side, catching a toe, or back or knee aches on one side are worth mentioning.

What I would not do is compare trouser hems. Mine told me I had a two-centimetre difference. The X-ray, when it was finally taken at my check, showed less than a few millimetres.

What helps

Most people need nothing beyond time and exercise, and those with a real difference that bothers them are usually helped by a shoe raise. For the apparent kind, the work is stretching the tight muscles around the hip and strengthening the ones that hold the pelvis level, guided by a physiotherapist. That is the same work that clears an early limp, and it is the reason supervised rehabilitation features so strongly in joint replacement guidance ⁴.

For a true difference, Versus Arthritis notes that a shoe insert or insole may be needed to correct it ⁵. A small raise can go inside the shoe; a larger one may need building into the sole. It is not glamorous, but it is effective, and many people stop thinking about it within weeks. Further surgery to correct leg length alone is uncommon, because a revision operation carries its own risks, and it is generally kept for a large difference causing real problems despite these simpler measures. The wider picture of what can go wrong after a hip replacement, and how uncommon most of it is, is in hip replacement risks and complications.

When to raise it with your team

Mention a feeling of uneven legs at your follow-up appointment, and get in touch sooner if something changes suddenly. An apparent difference in the early weeks is common enough that most teams expect to be asked about it, and there is no need to panic about it at home. But a leg that suddenly looks shorter or turned, especially with pain or difficulty bearing weight, is different: that can be a sign of dislocation and needs urgent attention the same day.

For me, the worry I had written down for my six-week check had answered itself before I got there. If yours has not, ask. A measured answer is better than another fortnight of staring at hems.

This is general information from my own experience, checked for accuracy, and not medical advice. Whether a leg length difference after your operation is real, and what to do about it, is a question for the surgeon and physiotherapist who can examine you.