Exploring the link between joint injury and osteoarthritis

25 June 2021

Osteoarthritis is the most common form of arthritis, affecting approximately 8.5 million people in the UK. It remains by far the commonest reason for costly joint replacement.

It’s well known that joint injury can increase the risk of osteoarthritis developing, however it’s not currently possible to predict who will develop problems after injury and who won’t.

Our researchers at the Centre for Osteoarthritis Pathogenesis Versus Arthritis wanted to take a closer look at this well-known association.

They 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.

Dr Fiona Watt, the lead researcher of the study 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”.

What did our researchers do?

The researchers recruited 150 people between the ages of 16 and 50 who had experienced an acute knee injury within the last eight weeks.

An acute knee injury means a sudden injury to the knee which damages structures within the knee. This can happen when people fall badly or twist their knee during normal daily activities, or in other types of trauma, like road traffic accidents.

These injuries are also common in sporting activities, such as footballers twisting their knee during a tackle playing football.

In any ‘acute’ case, the injury is bad enough that the person cannot walk normally afterwards for at least 24 hours, usually associated with some swelling in the knee.

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 knee 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.

What did researchers find?

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 in synovial fluid were also measured at the time of injury (rather than the blood), which added to the ability to predict knee symptoms at two years. 

Interestingly, the team also saw that what was seen on X-ray (i.e. structural differences to the knee after two years) often did not match up with the knee symptoms that people were self-reporting. For example, someone experiencing large amounts of pain, but with little change seen on X-ray or vice versa.

Understanding this relationship better, particularly early on in the disease, is really important in studying osteoarthritis and providing the right treatment at the right time.

What do the findings tell us?

This research shows that there are potentially ways to measure and predict how likely somebody is to develop osteoarthritis after knee injury and leads us to ask more about what individual factors might predict how a person will respond to injury.

Dr Neha Issar-Brown, Director of Research at Versus Arthritis said: “Osteoarthritis affects millions of people making it the most common type of arthritis in the UK. However, inability to predict how the condition will develop and progress causes a huge strain for the people living with the condition and incurs huge costs for the NHS.

Any research that may make it possible to predict if a risk factor – in this case joint injury - will lead to osteoarthritis is much needed and truly exciting. Not only will it help clinicians to provide early, preventative treatments, it may help reduce the uncertainty and anxiety associated with the condition and give people greater control of managing their future health. The results need to be confirmed in larger studies, but the findings of Dr Watt’s and colleagues are a positive step towards prediction and early detection but also towards understanding the complexity of factors that may cause osteoarthritis.”

What are the next steps for the study?

The research team continued to monitor participants of the study for a further three years and the five year follow up is complete and under analysis. This should allow them to look further at those who have developed clear signs of osteoarthritis and the risk factors for this.

The long-term aim would be to develop a tool or questionnaire that calculates people’s risk of future osteoarthritis at the time of an injury, but we are still some way off this yet.

If we can predict those likely to develop osteoarthritis, then we can begin to look at how we might intervene early to prevent this from happening.

Why is research like this important?

Former professional rugby player, Ben Lonergan, 34, now works as a rugby coach. In 2013, he was injured in a ruck whilst playing rugby and badly ruptured both the anterior cruciate ligament (ACL) and medial collateral ligament (MCL) in his left knee. He had surgery within two weeks of the injury and signed up as a participant on the study.

I still remember everything about the injury, it’s stuck with me. I knew instantly that I’d badly damaged the knee ligaments, as I heard them both snap.

I was fortunate enough to be referred to Mr Andy Williams for surgery and it was him who told me about Fiona’s study. I thought it was a great opportunity, especially given it could potentially help identify people at greater risk of developing osteoarthritis later in life from injury.

My knee has been okay since I had the surgery, I was able to go back to playing rugby after I recovered and I’m still very active now. However, I’m convinced I’ll get arthritis later in life, because I’ve done a lot of damage to the joints and the cartilage in my knee. 

As you get older, and you want to have kids and lead a normal life without pain or complications, the longevity of your joints and general health becomes way more important. If this study could help predict the likelihood of further damage from osteoarthritis happening, and there were ways to prevent this early on, then that would be amazing for so many people.”

This research was funded by Versus Arthritis. Dr Fiona Watt is also funded by a UKRI Future Leaders Fellowship. You can read the research article in full in the Lancet Rheumatology.

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