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 joined at an angle, with a twist, or slightly shorter than before. It is not the same as a non-union, where the bone does not heal at all. In malunion, the bone is solid. It is just not quite straight.

This can happen for several reasons. The first fracture may have been complex, with many pieces that were hard to line up perfectly. Sometimes the bone shifts slightly inside a plaster 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 very good at adapting. But over months or years, that small change in the shape of the bone 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 injured in the first place. Because the shape of the bone has changed, the joints above and below take extra stress. These are the patterns people often describe.

If one leg feels shorter after a break, it is worth looking into. 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. Arthritis can develop in a joint that was otherwise healthy.

The body's adjustment does not stop at the knee. Your hip changes its angle. Your pelvis may tilt. Your lower back adjusts further. This is why people with a badly healed broken leg sometimes develop hip or back pain that seems to have nothing to do with the first injury. Understanding lower limb alignment helps make sense of these connected problems.

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

A standing, weight-bearing scan shows the true alignment of your leg in real conditions, with gravity pulling and your muscles working. When you lie down for a standard X-ray or CT scan, the muscles relax and the joints decompress. 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 whole leg in one standing image, from the hip joint to the ankle, in 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 join separate images together, which can introduce errors.

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

At ScanAlign, standing EOS imaging in London, you stand naturally during the scan. So the image shows 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 hard 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. The options depend on how severe the deformity is and where it is. But they broadly fall into two paths.

• Conservative management. Physiotherapy to strengthen the muscles around the affected joints, orthotics or shoe raises to make up for a length difference, and changes to activity to manage symptoms.
• Corrective osteotomy. A surgical procedure where the bone is carefully re-cut and realigned to restore a more normal axis. It is planned using precise measurements from imaging. This 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 take the results back to your specialist at home.

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.

Common questions about malunion and leg alignment