Why Does a Badly Healed Fracture Change Your Leg Alignment?

What is malunion and how does it happen?

Malunion is the medical term for a fracture that has healed, but in the wrong position. The bone may have knitted at an angle, with a twist, or slightly shorter than it was before. It is not the same as a non-union, where the bone fails to heal at all. In malunion, the bone is solid. It is just not quite straight.

This can happen for several reasons. The original fracture may have been complex, with multiple fragments that were difficult to align perfectly. Sometimes the bone shifts slightly inside a cast or splint while it heals. In other cases, the alignment looked acceptable on early X-rays but the long-term position turned out to be just enough to matter.

You might not notice a problem at first. The body is remarkably good at adapting. But over months or years, that small change in bone geometry redirects the forces passing through your leg with every step you take.

What are the signs of a deformity after a fracture?

The most common sign is persistent or worsening pain in a joint that was not originally injured. Because the bone shape has changed, the joints above and below take on extra stress. Here are the patterns people often describe.

If you notice that one leg feels shorter after a break, that is worth investigating. A difference in leg length, even a small one, changes how your pelvis sits and how your spine responds. You can read more about leg length discrepancy and the knock-on effects it can have.

How does a malunion affect the rest of your leg?

Your leg works as a connected chain. The hip, knee and ankle are designed to share load in a very specific way, along what is called the mechanical axis. Think of it as an invisible plumb line running from the centre of your hip joint to the centre of your ankle. When the bones are straight, weight passes evenly through the middle of the knee.

A malunion shifts that line. If a shinbone healed with an inward angle, the axis moves to the inner edge of the knee. That side of the joint now carries far more load than it was designed for. Over time, cartilage wears unevenly and arthritis can develop in a joint that was otherwise healthy.

The compensation does not stop at the knee. Your hip adjusts its angle. Your pelvis may tilt. Your lower back compensates further. This is why people with a badly healed broken leg sometimes develop hip or back pain that seems completely unrelated to the original injury. Understanding lower limb alignment helps make sense of these connected problems.

Why does a standing scan show malunion more clearly than lying down?

A standing, weight-bearing scan shows the true alignment of your leg under real conditions, with gravity pulling and your muscles working. When you lie down for a standard X-ray or CT, the muscles relax, the joints decompress and the bones can shift into a position that looks better than it really is. The functional deformity, the one you actually walk on, can be hidden.

An EOS scan captures your entire leg in one standing image, from the hip joint to the ankle, on a single exposure. This means your specialist can see the full mechanical axis and measure exactly where it has shifted. There is no need to stitch together separate images, which can introduce errors.

EOS also uses about 90% less radiation than a standard X-ray, around ten times less. That matters if you need follow-up scans to track changes or plan a corrective procedure.

At ScanAlign, standing EOS imaging in London, the scan is done while you stand naturally, so the image reflects how your body actually carries its weight every day.

What can be done about a badly healed fracture?

The first step is getting an accurate picture of what has changed. Without a full-length, weight-bearing image, it is difficult to know exactly how much the alignment has shifted and how it is affecting the joints around it.

Once the deformity is clearly measured, your orthopaedic surgeon can decide on the best approach. Options vary depending on the severity and location, but they broadly fall into two paths.

• Conservative management. Physiotherapy to strengthen the muscles around the affected joints, orthotics or shoe raises to compensate for a length difference, and activity modification to manage symptoms.
• Corrective osteotomy. A surgical procedure where the bone is carefully re-cut and realigned to restore a more normal axis. This is planned using precise measurements from imaging, which is why accurate data matters so much.

ScanAlign does not provide treatment. It provides the detailed alignment imaging that helps your surgeon or physiotherapist make the right decision. If you want to see exactly where you stand, you can book a full-leg alignment scan and bring the results to your specialist.

Frequently asked questions about malunion and leg alignment