Rare disease research reveals new cause of osteoarthritis

A new study into a rare disease has led to the discovery of a hitherto unknown mechanism of joint destruction that could be a key cause of osteoarthritis.

The University of Liverpool and Queen Mary University of London research involved the assessment of the hip of a man with the genetic condition alkaptonuria, a metabolic disease in which homogentisic acid accumulates in joint cartilage, changing its physical properties.

It was found that high-density mineralised protrusions (HDMP) – which have only been seen before in horses – could be found in cracks in the joint cartilage. When they snap off, this creates sharp particles that grind against healthy tissue, eroding it away.

The team then studied eight hips donated for research by people with osteoarthritis and found the same results.

Professor Jim Gallagher, from the university's institute of ageing and chronic disease, said: "Studying a rare illness like alkaptonuria is a worthwhile project in itself, but it can also help with new insights into much more common diseases."

Osteoarthritis is the most common type of arthritis in the UK, usually developing in people over 50 years of age.