New study sheds light on link between joint injury and osteoarthritis

Researchers investigated the factors underlying the association between acute knee injury and osteoarthritis, the most prevalent form of arthritis.

Osteoarthritis affects approximately 8.5 million people in the UK and is the commonest reason for joint replacement. 

While previous research has established that joint injury can increase the risk of osteoarthritis, it is not currently possible to predict whether or not an individual will develop the condition as a result.  

A team led by Imperial’s Dr Fiona Watt (formerly based at the Kennedy Institute of Rheumatology in Oxford) set out to better understand this association and to investigate whether certain factors at the time of injury might explain an individual’s likelihood of developing osteoarthritis. 

Dr Watt explains: “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”.  

The findings of the study, supported by funding from Versus Arthritis, have now been published in The Lancet Rheumatology. 

Investigating the impact of joint injury  

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

An acute knee injury is defined as a sudden injury that 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.  

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.  

Two years after 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 per cent of people who took part in the study were showing signs of knee osteoarthritis two years after injury. This is significant, given the age range of the study’s participants. 

Key factors  

The findings point to three key factors 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.   

Next steps 

Better understanding the association between joint injury and osteoarthritis, particularly in its early stages, is vital to advancing research into the condition and ensuring that the right treatment is provided at the right time. 

The study’s findings suggest there are potentially ways to measure and predict how likely someone is to develop osteoarthritis after a knee injury. The research also paves the way for further investigation into the individual factors that 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.” 

The study team continued to monitor participants of the study for an additional three years, and the five-year follow up is now complete and under analysis. This should enable the researchers to look in more depth at those who have developed clear signs of osteoarthritis and the associated risk factors. 

In the long term, the team are aiming to develop a tool or questionnaire that calculates an individual’s risk of future osteoarthritis at the time of an injury, but further studies are needed to support this work. 

‘Clinical and molecular associations with outcomes at 2 years after acute knee injury: a longitudinal study in the Knee Injury Cohort at the Kennedy (KICK)’ by Cesar Garriga et al. is published in The Lancet Rheumatology 

This article was adapted from materials provided by Versus Arthritis.