Look after your knees for another five years and you could benefit from treatment that will keep joints functional for longer, writes Jill Margo.
If you can keep your ailing knees in reasonable shape for another five years, you may benefit from the renaissance currently underway in our understanding of osteoarthritis.
This disease is characterised by a loss of the cartilage that caps the ends of bones in joints such as the knee, the hand and the back.
As there is no known way to restore cartilage, osteoarthritis remains the last big disease for which there is no treatment.
But there is hope on the horizon and there are ways to protect your knees until some of this hope materialises. (see box)
Hundreds of thousands of Australians live with osteoarthritic knees. Some have discomfort, some have pain and some have restricted movement.
Traditionally, this has been seen as a disease of the cartilage due to wear and tear. Much of the research focus has been on understanding what goes wrong in the cartilage.
“But now we know it’s actually a disease of the whole joint, “says Flavia Cicuttini, one of Australia’s leading authorities on osteoarthritis.
“This disease is characterised by profound bone changes associated with progressive loss of cartilage, so that at the end stage there is bone on bone.”
The misconception about its origins hampered past research, says Cicuttini, a professor at Monash University and head of rheumatology at the Alfred Hospital in Melbourne.
“Knee osteoarthritis is not one disease. It is a failed joint with many different pathways that can result in this.”
This new understanding has emerged from fifteen years of research, across the world, using magnetic resonance imaging.
Compared to traditional X-rays, MRI provides images that are much richer in detail and enable researchers to study knee joints at very early stages of damage.
Although knees do wear with age, Cicuttini says osteoarthritis is not inevitable and “good looking” cartilage can be found in 90-year-olds.
“Preserving cartilage is the holy grail of osteoarthritis. I believe in the next five years we will start to see medicines that will slow the progression of osteoarthritis.”
Currently, all we have are anti-inflammatories and pain killers that target the symptoms, not the cause. When the disease becomes unmanageable, the next step is a knee replacement.
In 2014, some 47,500 first time total knee replacement procedures were performed in Australia. These devices don’t last forever and Cicuttini says a second replacement is usually far less successful than the first.
She recommends delaying a first knee replacement for a long as possible, to increase the odds that it will last your remaining years.
Common wisdom holds that if you carry extra weight you automatically increase the pressure on your knees.
It is estimated that a force of two to six times your body weight may be exerted across each knee depending on how you are moving. It’s lower when you walk across a flat surface and highest when you squat.
But this is only a part of the picture. Although weight does exert mechanical pressure on these joints, Cicuttini says it depends on what makes up the weight.
Two men may each have a body mass index of 30 kg/m2, but while one has a very high proportion of muscle, the other may have a very high proportion of fat.
There is evidence that while muscle protects the knee, an increase in fat mass leads to a faster loss of knee cartilage and an increased likelihood of joint replacement.
She says fat delivers a double hit. It increases mechanical pressure and has an inflammatory effect too.
Body fat is not inert. It’s not just a layer of indolent energy you carry around and live off in lean times. Rather, it is metabolically highly active and produces inflammatory molecules that can damage joints, including the knee.
Long before symptoms emerge, inflammatory molecules are silently at work in the knee, causing joint changes that undermine the cartilage.
This makes the joint more vulnerable to the long-term mechanical pressures of carrying excess fat.
The joint becomes squishy and a vicious cycle is established with further joint damage created through both inflammation and loading.
In a recent editorial in the Medical Journal of Australia, Cicuttini says while obesity is a well-recognised risk factor for osteoarthritis, the fact that people get the condition in their hands too, shows it’s not just about loading.
“Given that we do not walk on our hands, an effect of obesity through loading of the joints cannot be the whole explanation.”
Research has shown increased weight is associated with early articular cartilage damage, well before joint symptoms develop.
Previously it was not unusual for men, who liked to run, to be told to push through their knee osteoarthritis. It was explained that minus the cartilage, their bones would polish each other and all would be well.
While having bone on bone is not necessarily painful, Cicuttini says it would be unwise to jog with this condition.
For a 50-year-old executive who is used to taking control and doesn’t want to relinquish running, she predicts he’ll do it for a couple of years – feel good about it – and then probably need a knee replacement earlier than he might otherwise have.
Pounding on an injury accelerates damage and cartilage loss. She recommends he moves to swimming or cycling, saying, with prudent exercise he can probably stave off a replacement knee by another five years.
To men of 35 with no knee pain, she exhorts them to guard against injury and be very careful about not gaining weight. This sounds like a motherhood statement, but most Australian adults are gaining weight.
To both she advises they maintain muscle strength in their lower body but particularly in their quadriceps. These large muscles down the front of the thigh help to maintain the strength and stability of the knee.
When large population studies suggested people on cholesterol lowering drugs, statins, had a slower progression of their osteoarthritis, Cicuttini and her team decided to test this. The trial is now underway.
Together with colleagues they are also trialling bisphosphonates, drugs already in wide use to treat the bone weakening disease, osteoporosis. They are investigating if a single injection of this drug, given once a year, could slow knee osteoarthritis.
Previously the team investigated Vitamin E and found it was not useful. There are now plans to investigate krill oil.
She says some supplements are safe, well tolerated and may help to improve symptoms. None, however, rebuild cartilage.
There is evidence very large doses of fish oil have an anti-inflammatory effect and some studies have shown chondroitin sulphate may help too.
While there are controversial suggestions that glucosamine sulphate may slow the progression of osteoarthritis, there is no clear proof.
FIVE SIMPLE WAYS TO PRESERVE KNEE CARTILAGE
1. Gain no more weight.
2. Lose fat if you are carrying too much of it.
3. Don’t let your muscles waste, particularly your quadriceps.
4. Exercise sensibly and change sport if you have a knee injury.
5. Diligently avoid injury during exercise