Osteoarthritis affects approximately one third of the population over 60 years old, and can cause significant pain and disability. Many have anecdotally noted that knee arthritis seems to be becoming more common, but is it really, and if it is, then why?
A recent Harvard study examined the knees of over 2000 skeletons ranging in time from prehistoric periods to the present post-industrial times, looking for signs of knee osteoarthritis. They found that the skeletons from post-World War II were twice as likely to develop knee osteoarthritis than the others. This result was expected, and many have assumed the incidence of osteoarthritis has been increasing in recent years because people are now living longer and also becoming more obese. The researchers had information on age and body mass index for most of the skeletons from the early 1900’s and onward, however, and when they controlled for these factors, they were surprised to still find double the occurrence of knee osteoarthritis. This means living longer, and weighing more can’t be the primary causes behind the rise in knee osteoarthritis.
With the occurrence of knee osteoarthritis increasing so quickly, and not related to age or weight, it is likely in large part due to environmental factors. Perhaps more time standing and walking on hard surfaces, and choice of footwear that increases the loading on the knees (e.g. high heels) could be partially responsible, but it is thought that inactivity could be a major cause osteoarthritis. We know that average activity levels have decreased dramatically in the last 50 years. By decreasing our activity levels, our cartilage becomes thinner and our muscles are weaker, offering less ability to act as shock absorbers and protect the joint from outside forces. This might cause earlier breakdown of the cartilage on our joint surfaces, thus accelerating the onset of osteoarthritis.
So what can we do to prevent knee osteoarthritis? The best advice seems to be keep your muscles strong, and keep moving! This fits within the Canadian Physical Activity Guidelines of 150 minutes of moderate-to-vigorous exercise per week to gain health benefits.
If you have osteoarthritis related questions, or are interested in becoming more physically active, talk to your Physiotherapist today!