Blood test could detect osteoarthritis in the knees eight years before it appears on X-rays

A blood test could detect osteoarthritis in the knees up to eight years before it appears on X-rays – leading to hopes for a preventative treatment.

The condition – thought to affect more than five million people in the UK – occurs when cartilage in the knee joint breaks down, causing it to become painful and stiff.

The disease is usually not found until it has already caused structural damage to the joint.

Surgery has been the only option available for many, with more than 120,000 knee replacements performed in the UK each year.

But the new test, which can spot the condition years in advance, could provide a ‘window of opportunity’ to restore joint health.

Professor Virginia Kraus, from Duke University School of Medicine, said: ‘Currently, you’ve got to have an abnormal X-ray to show clear evidence of knee osteoarthritis, and by the time it shows up on your X-ray, your disease has been progressing for some time.

‘What our blood test demonstrates is that it’s possible to detect this disease much earlier than current diagnostics permit.’

The main symptoms of osteoarthritis are joint pain, stiffness and problems moving the joint. Some people also experience swelling, tenderness and grating or crackling sounds when moving.

Almost any joint can be affected, but it most often causes problems in the knees, hips and small joints of the hands. The researchers analysed blood serum from 200 women – half diagnosed with osteoarthritis and the other half without the disease.

The findings, published in the journal Science Advances, showed biomarkers – signatures in the blood – that distinguished the women with knee osteoarthritis from those without it.

The test caught signs of the condition up to eight years before many of the women were diagnosed by X-ray. 

‘This is important because it provides evidence that there are abnormalities in the joint that can be detected by blood biomarkers well before X-rays can detect osteoarthritis,’ Professor Kraus added.

‘Early-stage osteoarthritis could provide a window of opportunity in which to arrest the disease process and restore joint health.’

There are currently no cures for osteoarthritis, but the success of future therapies could hinge on identifying the disease early and slowing its progression.

The cause is unknown, but older age, obesity, and being a woman are thought to increase the risk.