Leg Length Discrepancy After Knee or Hip Surgery: Why It Happens and What to Expect

Many patients leave knee surgery with a better joint and a new puzzle: one leg now feels longer, shorter, or just different. If that sounds familiar, you are not alone. This guide focuses on leg length discrepancy after knee surgery, why it can happen, which types are temporary, and what the research says, and doesn’t say, about shoe lifts. (If your surgery was on the hip, our companion article on shoe lifts after hip replacement goes into that decision.)

Real difference or only a feeling?

First, figure out whether your legs are truly different lengths. After surgery, the answer can be “a little, but not for the reason you think.”

The Bruyère Health rapid review of leg length discrepancy and shoe lifts points out that leg length differences are common: 10 to 20% of patients evaluated for painful musculoskeletal conditions have one. So a difference may have been there before your operation, and it only became noticeable once the pain was gone and you started walking more evenly.

Why leg length discrepancy after knee surgery can occur

There is no single cause. Possible contributors include:

• A knee that does not fully straighten. The same Bruyère review reports that about 1 in 10 patients has a knee flexion contracture after total knee arthroplasty. A leg that cannot fully straighten can act as a shorter leg when you stand, even if the bones are the same length.
• Changes in alignment. Correcting a bowed or knock-kneed knee changes how the whole leg lines up, which can change how long it feels.
• Implant and bone differences. Replacing worn surfaces and removing damaged bone can change the length of the leg a small amount in either direction.
• Tight or weak muscles. Swelling, stiffness, and muscle guarding can tilt the pelvis during recovery.
• A hip, back, or foot that was already part of the pattern. Arthritis elsewhere can make one side behave as if it were shorter.

The size matters too. In the studies collected by Bruyère, the measured differences ranged from 0 to 45 mm, which is a wide range. Most people in clinical practice are at the smaller end.

What is often temporary

Early after surgery, swelling, stiffness, and an altered walking pattern can all create a sense of unevenness. As the knee moves better and the muscles recover, the feeling often settles. For the hip, eOrthopod notes that soft-tissue changes in the first six months may resolve on their own. Your surgeon can tell you whether a similar window applies to you. It is generally wise to hold off on permanent changes until your surgeon and physical therapist agree that recovery has levelled off.

Where shoe lifts fit in leg length discrepancy after knee surgery

A shoe lift is a common conservative option if a true difference remains after recovery. It is reversible, and it does not interfere with the joint. But it is worth being honest about the evidence:

• The Bruyère review rates the evidence for shoe lifts as very low quality.
• It found no studies of shoe lifts specifically after total knee replacement, and it notes disagreement about lifts above 20 mm.
• The wikiMSK reference likewise describes the evidence that lifts reduce pain and improve function as low quality, and suggests a partial correction, around 50%, as a reasonable starting point.

None of that means a lift cannot help you. It means the decision should be individual, cautious, and reviewed along the way. For a hip patient, a Mayo Clinic surgeon quoted in the Mayo Clinic Q&A says there is no medical reason not to use a shoe lift, and that stability matters more than exact equal leg length. The same practical thinking applies to the knee.

What a physical therapist may look at first?

Because a knee that does not straighten can mimic a short leg, a physical therapist assessing leg length discrepancy after knee surgery might check:

1. Range of motion. Can the knee straighten fully?
2. Pelvic level. Is one hip higher when you stand?
3. Strength and gait. Are you favouring one side?
4. True length. A block test or an X-ray, the methods Yale Medicine lists for diagnosis. HSS describes the same approach: the block method on examination, and standing, full-length X-rays to confirm it.

If the issue is stiffness, exercises may help more than a lift. If a true difference remains, a lift may be added to the plan.

Questions to bring to your follow-up visit

A follow-up appointment is the best time to raise leg length discrepancy after knee surgery. Consider asking:

1. Is my knee straightening as fully as expected?
2. Is the difference I feel real, and how large is it?
3. How long should I wait before deciding on a lift?
4. Could my hip, back, or foot be adding to the problem?
5. Which exercises should I keep doing while I wait?

Living with a small difference

Not every difference needs treatment. As Yale Medicine notes, mild differences generally don’t affect health, and HSS says a difference under 10 mm is often well tolerated. If your gait feels comfortable and your joints are not complaining, a small residual leg length discrepancy after knee surgery may simply be part of your new normal. The aim of care is comfort and function, not a perfect measurement.

Warning signs to take seriously

Contact your surgeon rather than adjusting anything yourself if you notice:

• New or increasing pain in the knee, hip, or back
• Swelling, warmth, or redness around the knee
• A sudden change in how you walk
• A knee that is getting stiffer rather than looser

A lift will not fix those, so do not assume leg length discrepancy after knee surgery is the explanation.

If a lift is recommended

Your clinician may give you a number, usually a modest amount. You can use our measurement tool and the standing block test guide to record your own readings and bring them to the appointment. They support the conversation, but they do not replace a clinical exam.

A small correction may fit inside the shoe, but many shoes have little room, and American Heelers limits an internal insert to about a quarter of an inch. For more height, the lift is built onto the sole. Our guide to internal and external shoe lifts explains how to choose, and the article on whether shoe lifts can fix a short leg covers the basics.

Since 2007, American Heelers has developed practical expertise across thousands of footwear designs, accounting for differences in outsole composition, heel construction, sole flexibility, shoe profiles, and individual correction measurements. These factors help determine the appropriate approach for sneakers, boots, formal footwear, golf shoes, and specialty designs.

Operating from Beachwood, Ohio, we serve Cleveland-area customers and those farther afield with footwear modifications tailored to specific structural and functional requirements.

Next steps

If a lift becomes part of your plan for leg length discrepancy after knee surgery, our custom shoe lifts are built into your own shoes, and no prescription is needed, although we encourage you to keep your care team informed. See the frequently asked questions, or place an order when you are ready.

This article is for general information and does not replace advice from your surgeon.