MRI Study Shows Weight Loss of at Least 10% Protects Knees
Losing weight prevents further damage to knee cartilage and joints.
An interview with Alexandra Gersing, MD and Thomas Link, MD, PhD
Being overweight is a major risk factor for a number of challenging health issues—including knee pain and osteoarthritis. But a newly released study may give overweight people the best reason yet for losing weight—preventing or putting off these potentially life-changing problems.
Results of a large, nationwide study revealed that overweight people who lost at least 10% of their body weight had the least amount of knee cartilage deterioration and pain. (Cartilage is the material that acts as a cushion between the bones in the knee and protects them from rubbing together and damaging each other.)
Knee osteoarthritis is one of the most painful types of degenerative joint disease and often leads to knee replacement surgery. "Once cartilage is lost in osteoarthritis, the disease cannot be reversed," noted Alexandra Gersing, MD, the lead investigator of the study in a recent phone interview with Practical Pain Management.
Dr. Gersing and her colleagues from the University of California, San Francisco investigated the relationship between weight loss and knee cartilage degeneration. According to the Centers for Disease Control and Prevention, more than a third of the population over 60 is affected by knee osteoarthritis. As part of the Osteoarthritis Initiative—a national research study funded by the National Institutes of Health (NIH)— the researchers had access to 506 overweight and obese patients.
“No previous studies about knee osteoarthritis have looked specifically at the quality of the cartilage until now,” Dr. Gersing said. An MRI was used to track changes in the cartilage over a four-year period and the before and after images revealed less cartilage deterioration in patients that lost the most weight (see Figure).
To qualify for the study that was initiated in 2004, patients either had to have osteoarthritis or risk factors for the disease. They ranged in age from 45 to 75 and were divided into three groups:
- A control group that lost no weight
- A group that lost some weight
- A group that lost more than 10 percent of their body weight
"Cartilage degenerated significantly more slowly in the group that lost more than 10% of their body weight, especially in the weight-bearing regions of the knee," Dr. Gersing said. "However, those with 5% to 10% weight loss had almost no difference in cartilage degeneration compared to those who didn't lose weight."
Of course, the researchers weren’t surprised that weight loss was beneficial. What surprised them was that the amount of weight lost mattered. “Ten percent or more is the magic number,” researcher Thomas Link, MD, PhD, explained during the same interview. “Losing less than that didn’t make much difference in terms of cartilage preservation.”
Pain levels were also evaluated in the study. Dr. Gersing said the patients with the most weight loss also experienced the most pain relief—another beneficial result.
What is Knee Osteoarthritis?
If you have knee osteoarthritis, the swelling and stiffness you experience can turn everyday activities like walking or going up and down stairs into painful moments. The condition can be a source of work absenteeism and causes many people to become disabled.
The knee is made up of three bone—the thigh bone (femur), shin bone (tibia) and knee cap (patella)—and is one of the strongest joints in the body. Cartilage enables movement and helps keep the knee stable. Age, overuse and obesity can wear away the cartilage. As it deteriorates, it becomes thin and provides less protection. Damage and bone spurs form as a result.
Why Losing Weight is Key to Preventing Pain
Since cartilage is a fibrous tissue and lacks its own blood supply, regeneration isn’t possible. Unfortunately, damage to the cartilage isn’t easily repaired by the body either.
Today, knee replacement surgery is still the main remedy for the problem though cartilage stem cell growth and transplantation may be viable options in the future. The doctors pointed out that one of the drawbacks of joint replacement is that they don’t last forever and additional surgeries are often less successful. “Joint replacements typically last 10 to 15 years,” Dr. Link explained. “With people living longer, additional knee replacement surgery would more than likely be necessary with less optimal results.”
In overweight people, artificial joints present many complications, according to Dr. Link. “Artificial joints can get infected more easily. And, future replacements are often much more difficult due to more bone loss from aging, joint loosening and other kinds of damage that compromise the procedure.”
Preserving cartilage is one of the best ways to avoid knee replacement surgery and spare yourself pain. Going forward the researchers hope that health practitioners will strongly encourage their overweight patients to lose a significant amount of weight—not just a few pounds.