For the study, which is published in the International Journal of Obesity, the researchers examined 68 people who had surgery to repair or remove a torn meniscus, which is the cartilage in the knee that acts as a cushion between the shinbone and the thighbone. When this occurs, your wellbeing is at risk of developing osteoarthritis, a condition in which your cartilage breaks down, causing levels of pain, swelling and stiffness that make it difficult, over time, to move your joint or put weight on it.
According to principal investigator Robert H. Brophy, a sports medicine specialist and associate professor of orthopaedic surgery, ‘Having a tear in the meniscus is associated with an increased risk of developing osteoarthritis later in life. Some studies have suggested that more than 50% of people with a meniscus tear will go on to develop arthritis 10 to 20 years later, but we don’t precisely understand how one leads to the other.’
Brody, along with M. Farrooq Rai, a postdoctoral research scholar in orthopaedic surgery, led a team which analysed the activity of 28 genes related to obesity, ageing, and the secretion of inflammatory substances in meniscus tissue. He explained, ‘We know there’s a mechanical relationship. People who are obese have increased pressure and force on the knee joint. And older people have more wear and tear on the joints. But we wanted to see whether something else is going on that may accelerate the risk for osteoarthritis.’
The team discovered one obesity-related gene and four ageing-related genes behaving abnormally in torn meniscus tissue, and low activity in these genes contribute to the disease by leaving the tissue without enough of the proteins necessary for the meniscus to function normally, and increasing inflammation levels. Co-investigator Linda J. Sandell, a professor of orthopaedic surgery, commented, ‘In general, I think we can say that the inflammatory molecules we see in the tissue are not good. The meniscus is a stable, slowly changing tissue. But if it’s overstimulated, that usually means it’s being irritated in some way.’
‘What we don’t know at this point is whether the meniscus is irritated because it was torn by injury or whether it’s responding to something else. It’s even possible that the tissue tore because it already was in a pre-osteoarthritis condition,’ she noted. ‘We’re beginning to learn that the meniscus itself is manufacturing things that could degrade tissue in the knee, so it may be an active player in osteoarthritis. Unfortunately, many drug companies aren’t excited about developing drugs to inhibit osteoarthritis until we can show that it’s possible to detect it early.’