British experts have found a natural material, previously only seen in horses, in the hip joints of patients.
It forms sharp, dense fragments that grind away healthy cartilage, making the condition worse. Some 8.5 million Britons suffer osteoarthritis, the most common form of the condition.
It is caused by wear and tear on joints where the cartilage that cushions movement is worn away. Bones then come into contact with each other and the friction makes joints swollen and extremely painful.
At the moment, treatments only relieve the symptoms.
One recently approved drug can slow its progress but osteoarthritis is still incurable and often requires costly hip or knee replacements.
The breakthrough was the result of work by researchers at Liverpool University and Queen Mary University of London.
“We have discovered a previously unrecognised mechanism of cartilage destruction in human hip joints. This discovery could certainly lead to new treatments.”The scientists looked at the hip of a man with the genetic condition known as alkaptonuria, which causes homogentisic acid to accumulate, causing changes to joint cartilage. The study found the presence of high density mineralised protrusions (HDMP), previously only seen in horses.
These protrusions are caused as the body acts to fill in cracks in joint cartilage and can snap off and grind against healthy tissue. The team then found the same HDMP in eight hips donated for research by people with osteoarthritis.
Professor Gallagher, of the university’s Institute of Ageing and Chronic Disease, said: “The discovery of HDMP in humans means that for the first time we are seeing an important mechanism in the process which causes the disease. In effect these small, sharp particles could act like an abrasive powder scouring the surfaces of the joint.
“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. This is a case in point and because of our work on alkaptonuria we are now able to add a new piece to the puzzle of an illness that affects millions.”
Natalie Carter, head of research liaison and evaluation at Arthritis Research UK, said: “We were excited to hear about the research developments in Professor Gallagher’s lab.
“New findings that show brittle protrusions develop on the bones of people with osteoarthritis shines a light on the processes that cause arthritis, and initiate joint damage. We are hopeful that understanding the processes causing the disease will ultimately lead us towards new treatments for osteoarthritis and in the future a cure for this painful and debilitating disease.
“Arthritis Research UK funds research into musculoskeletal conditions, including a number of rare diseases. Although these conditions affect a smaller number of people they can be very severe.
“One clear message from the research led by Professor Gallagher is that there is value in researching these rarer disorders as they can reveal insights into other more common diseases. This research provides hope for people living with the pain of osteoarthritis in the UK, as well as other rarer conditions.”
The NHS spends about £5.2billion a year treating osteoarthritis and carries out 77,000 knee and 66,000 hip replacements.
A fifth of people over 45 suffer from osteoarthritis in a knee.
Ageing and obesity are the most common contributing factors. And with both on the rise, the number of people in the UK consulting a GP about osteoarthritis of the knee could rise from 4.7 million in 2010 to 8.3 million by 2035, according to estimates.