Osteoarthritis (OA) is the most common form of arthritis, affecting approximately 8.5 million people in the UK. It is by far the most frequent reason for costly joint replacement.
It has been shown that joint injury can cause OA in some people, but it is not currently possible to predict who will develop problems after injury and who won't.
Dr Fiona Watt, from the Kennedy Institute of Rheumatology at NDORMS took a closer look at this well-known association and the results have been published in The Lancet Rheumatology.
Supported by funding from Versus Arthritis, Fiona and a team of researchers hoped to understand whether there was anything happening at the time of injury, which might explain whether somebody was more likely to develop osteoarthritis in the future.
Fiona said: "Joint injury is an important opportunity for us to understand risk factors and processes occurring early on in osteoarthritis development. This may allow us to identify people at higher risk and aim to prevent later disease. We set up this study because our laboratory work had told us that the trauma to joint tissues at the time of a joint injury causes inflammation. We wanted to understand if the level of this response in a joint at the time of injury was an important factor in an individual's risk of developing osteoarthritis in the future".
They recruited 150 people between the ages of 16 and 50 who had experienced an acute knee injury within the last eight weeks.
At the start of the study, close to the time of injury, the research team measured markers of inflammation in both the blood and synovial fluid (the lubricating fluid inside the joint) of the injured knee.
Then two years on from the initial injury the team looked at:
- Patient reported symptoms such as knee pain
- and structural changes to the knee joint on X-ray.
The team found that large numbers of people from the study were experiencing ongoing knee pain or issues with knee functioning at two years. The researchers also saw that around 15-20% of people who took part in the study were showing signs of knee osteoarthritis two years after injury. This is substantial, given that most of the people who took part in the study were a young age.
There were three key factors measured in clinic that affected the outcome for people who had experienced a knee injury:
- How bad knee symptoms were at the time of injury
- Presence of large amounts of blood in the joint at the time of injury
- Swelling in the knee joint (which can also be caused by blood in the joint, or just extra knee fluid)
This is the first time it has been found that measuring how much blood is present in the joint can be a useful risk factor for future knee osteoarthritis symptoms across a range of knee injuries.
The levels of two inflammatory markers measured in synovial fluid at the time of injury (rather than the blood) added to the ability to predict knee symptoms at two years.
Interestingly, the team also saw that what was seen on X-ray (ie structural differences to the knee after two years) often did not match up with the knee symptoms that people were actually self-reporting, for example, someone experiencing large amounts of pain, but with little change seen on X-ray or vice versa.
This research shows that there are potentially ways to measure and predict how likely somebody is to develop osteoarthritis after knee injury. With further research it may be possible to develop ways to intervene at the time of injury or introduce potential preventative measures to stop the onset of osteoarthritis.