Daily Bulletin 2017

How Weight is Lost Can Slow Knee Cartilage Degeneration

Wednesday, Nov. 29, 2017

Once cartilage is lost in osteoarthritis (OA), particularly in the knees, the disease cannot be reversed. The question of whether or not the degeneration could be slowed by different weight-loss regimens was a hypothesis investigated and shared in a Tuesday session.

"We know that losing weight benefits knee health by decreasing weight-bearing pressure and reducing the knee joint load," said Alexandra S. Gersing, MD, from the University of California, San Francisco. "What we did not know was the effect of weight loss on osteoarthritis specifically and the inflammatory markers of the disease."



The study looked at 760 male and female patients with a body mass index greater than 25 who were enrolled in the Osteoarthritis Initiative (OAI), a U.S.-based study focused on the prevention and treatment of knee osteoarthritis. The patients all had risk factors for OA or had been previously diagnosed with mild to moderate OA.

Patients were categorized into groups according to the amount of weight they were asked to lose over a 48-month period versus a group with stable weight. They were further categorized into groups regarding the weight loss method — diet and exercise, diet only or exercise only.

Changes in the right knee were assessed at baseline, 48-, and 96-months using 3T MRI. T2 relaxation time changes of cartilage composition, including laminar and texture analysis as well as morphological knee abnormalities, were assessed with Whole-Organ Magnetic Resonance Imaging Score (WORMS). These times were analyzed using mixed random effects models to calculate associations between the amount of weight loss and the regimen used.

In the weight loss groups overall, progression of cartilage WORMS was significantly lower than in the controls over 96 months. Patients who lost weight showed significantly less T2-value increase in the bone layer of all compartments compared to those with stable weight, suggesting less cartilage degeneration over 96 months.

"It is a known fact that weight loss means less pressure on the knees," Dr. Gersing said. "Patients with weakened knees who experienced pain or a disability — or who compensated for these things with a change in gait — probably felt better after weight loss and therefore moved a bit more, making slight gains in preventing further cartilage loss."

Rates of increase in cartilage T2 were lowest in the diet and diet and exercise groups compared to the control group, while weight loss through exercise alone showed no significant difference in change of T2 over the 96 months.

Knee joint of a patient without weight loss (A) showing severe cartilage defects after 48 months, and intact knee joint of a patient with a substantial amount of weight loss (B). Click ot tap to view larger

This study adds to the information about which types of weight loss are most beneficial for patients who need to lose a significant amount of weight to slow the progression of knee cartilage degeneration.

"Other lifestyle changes are needed, beyond exercise, to reduce the risk of osteoarthritis or prevent further losses in the beginning stages of the condition," Dr. Gersing said. "Patients and doctors should work together to develop individualized therapy strategies and lifestyle interventions in order to prevent future degeneration."

Tip of the day:

In CT contrast studies, lowering kVp can reduce both radiation and contrast dose.

The RSNA 2017 Daily Bulletin is owned and published by the Radiological Society of North America, Inc., 820 Jorie Blvd., Oak Brook, IL 60523.