Osteoarthritis (OA) is one of the leading causes of musculoskeletal pain worldwide and is currently an irreversible process. Because of this, identifying risk factors that lead to osteorarthritis may help us stop the process before it begins and therefore decrease the effect it has on individuals and society.
With this idea in mind, a recent study led by Aleksandra Turkiewicz of Lund University in Sweden was able to take a unique snapshot of data from 18 year old Swedish conscriptees in 1969 and compare it to osteoarthritis data for the same men from 1996 onwards in the hope of assessing the relationship between quadriceps strength and body weight in adolescent men and the risk of knee osteoarthritis by middle age.
Intrestingly, the result of the study was that men with stronger quadriceps during adolescence had a higher incidence of knee osteoarthritis by middle age. Not so surprisingly, it was also found that higher weight during adolescence was a strong risk factor for knee OA in later life.
On face value, this first finding appears to contradict traditional thinking that stronger quadriceps will provide greater support to the knee joint and therefore minimise wear and tear, so what’s going on here?
Although the authors have not discussed the possible reasons for their findings, there are a few things to consider before you stop your current gym program in the hope of preventing osteoarthritis in the future.
As well as quadriceps strength, the study compared data such as weight, parental education level, alcohol consumption, smoking status, adult occupation and knee injuries/surgeries. Unfortunately it wasn’t able to compare other potentially important variables such as sports/activity participation over the lifespan or the change in quadriceps strength over time. The study also only included men, as there was no comparable data for women in 1969 – further limiting the conclusions we can make.
It is therefore possible that some subjects may have had stronger quadriceps due to greater sports/activity participation as adolescents and then continued this higher level of participation throughout their life. This increased joint load over time could then have led to the increased incidence of osteoarthritis as they aged.
It is also important to note that during the initial assessments, the heavier subjects generally had stronger quadriceps. This makes sense – if you have more body weight to move around, your legs are going to be stronger. So is quadriceps strength really a risk factor for developing osteoarthritis? Or is just that increased weight is the real risk factor, with greater quadriceps strength just being normal for heavier people?
A better way to assess this could be to use a strength/weight ratio – divide the overall quadriceps strength by the weight of the individual – then we’d know whether having stronger or weaker quadriceps relative to total body weight has any effect on the incidence of osteoarthritis.
So overall, although it is interesting that the authors have found a higher incidence of knee osteoarthritis in men who had stronger quadriceps during adolescence, the results need to be interpreted with caution. We don’t have all the information so don’t stop your gym routine just yet!