Weight loss can preserve knee cartilage in obese people

Obese patients who lose a substantial amount of weight experience significantly slower degeneration of their knee cartilage.

The study found knee cartilage degenerated a lot slower in obese patients who lost over 10% of their body weight, especially in the weight-bearing regions of the joint.
Image credit: A. Gersing/UCSF

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.

They found those who lost more than 10% of their body weight had slower degeneration of their knee cartilage.

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.

MRI spots changes in cartilage quality 'even before it breaks down'

Fast facts about osteoarthritis

• Osteoarthritis affects over a third of American seniors
• It accounted for over 3 million hospitalizations in the US in 2011
• The disease occurs more frequently in women than men, especially after age 50.

Find out more about 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% 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% of their body weight, especially in the weight-bearing regions of the knee. However, those with 5-10% weight loss had almost no difference in cartilage degeneration compared to those who didn't lose weight."

Dr. Gersing says weight loss not only helps preserve the knee joint, but it also reduces the risk of developing osteoarthritis; he explains that together with moderate exercise, it is one of the best ways to prevent the disease.

The researchers are continuing to follow the group for another 4 years to find out what effect putting on weight may have on the knee joint.

They also plan to do a study to see how diabetes - which is closely linked to obesity - affects cartilage degeneration.

Meanwhile, from studies presented at a meeting of orthopedic surgeons earlier this year, Medical News Today also learned that obese patients have better joint replacement outcomes if they have weight-loss surgery before receiving a new knee or hip.

Written by Catharine Paddock PhD

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