Obese patients who lose a substantial amount of weight experience significantly slower degeneration of their knee cartilage. So says a study presented at the Radiological Society of North America (RSNA) meeting in Chicago, IL, on Monday. The researchers investigated the link between different amounts of weight loss and the progression of knee cartilage degeneration - as shown on magnetic resonance imaging (MRI) scans - in over 500 overweight and obese patients. Osteoarthritis - also known as degenerative joint disease - is where there is a progressive loss of the cartilage in the joint. The knee is a common site, and in many people, the disease progresses to the point where they need to have the whole knee replaced.
The risk of osteoarthritis increases with age. Obesity is also a risk factor because carrying extra weight puts added stress on joints like the hips and knees, and it increases inflammation-promoting proteins produced by fat tissue. Study leader Dr. Alexandra Gersing, from the Department of Radiology and Biomedical Imaging at the University of California-San Francisco (UCSF), says loss of cartilage in osteoarthritis cannot be reversed, but: "Obese patients who lose weight can slow down the progression of cartilage degeneration in the knee."
For their study, the researchers investigated the link between different amounts of weight loss and the rate of knee cartilage degeneration in 506 overweight and obese patients taking part in a nationwide study on the prevention and treatment of knee osteoarthritis. The study participants, who either had mild to moderate osteoarthritis or known risks for the disease, were put into three groups: those who did not lose weight (the controls), those who lost a little weight, and those who lost a substantial amount of weight (more than 10 per cent of their body weight). Over a 4-year period, the patients underwent MRI scans to see how osteoarthritis progressed in their knees.
Dr. Gersing explains that from the MRI measurements, they can see changes in cartilage quality at a very early stage, "even before it breaks down."
When the team analyzed how knee cartilage quality changed over the 4 years in the three groups, they found that weight loss appeared to offer a protective effect. Dr. Gersing says this appeared to be significant at higher levels of weight loss:"Cartilage degenerated a lot slower in the group that lost more than 10 per cent of their body weight, especially in the weight-bearing regions of the knee.

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