Osteoarthritis: Weight Loss Takes a Load Off Knee Cartilage

Neil Osterweil

February 14, 2014

Clinicians have long recommended losing weight to help ease the pain and discomfort of knee osteoarthritis (OA), and now there is evidence to back up that bit of medical wisdom.

In a study of 112 obese adults, Australian investigators found that weight loss was associated with a lower amount of cartilage volume loss in the medial tibia and an improvement in knee symptoms, whereas further weight gain had the opposite effect. The findings were published online February 11 in the Annals of Rheumatic Diseases.

"These results suggest that in obese people, weight change has a potentially disease modifying effect on both knee joint structure and symptoms. While weight loss is an important primary management strategy in obese individuals to reduce their knee symptoms and deleterious structural changes, avoidance of further weight gain must also be a management goal in obese individuals," write Andrew J. Teichtahl, MD, from Monash University and Alfred Hospital in Melbourne, Australia, and colleagues.

The authors note that although recent systematic reviews have shown improvements in knee OA after bariatric surgery or a nonsurgical weight loss program, hard evidence for the effect has been hard to come by.

"We know that the less tibial cartilage there is, the more knee pain there is, and loss of tibial cartilage predicts the need for knee replacement," senior author Flavia Cicuttini, MD, PhD, head of the musculoskeletal unit at Alfred Hospital, told Medscape Medical News.

"Although OA is a disease of the whole joint, articular cartilage loss is the hallmark of disease severity and progression. We know that loss of cartilage correlates with the severity of knee OA as measured using X-ray, so the worse the X-ray the less tibial cartilage there is. We use knee cartilage, and specifically tibial cartilage, because it allows us to examine the state of the joint in a very sensitive way — far more sensitive than X-ray," she said.

To see how weight change may affect the knee joint, Dr. Teichtahl and colleagues recruited 112 obese adults (body mass index ≥ 30 kg/m2) from weight loss programs and other sources in the community. They looked at change over time (mean follow-up, 2.3 years) in tibial cartilage volume and knee symptoms, as scored by the West Ontario and McMaster Osteoarthritis Index (WOMAC).

They found a relationship between percentage weight change from baseline and change in all subscales of the WOMAC index, including pain (β function, −1.8 mm; P < .01), stiffness (β, −1.6 mm; P < .01), and function (β, −6.9 mm; P < .01 ).

The relationship appeared to be linear, with every 1% of weight loss associated with a 1.2 mm3 decrease in the loss of medial tibial cartilage volume. Conversely, every 1% gain in weight was associated with 1.2 mm3 increase in loss of volume.

The association held up in multivariate analysis adjusted for age, sex, body mass index, time between scans, and baseline cartilage volume.

The authors note that although the study included only obese adults, the relationship between weight change and knee OA is likely to be seen in people with various body types.

Dr. Cicuttini said that although there is evidence to suggest that obesity is a risk factor for patellofemoral OA, they did not see a significant effect of weight loss on patellar cartilage volume.

"It may be that if the effect is smaller in that compartment, we would need larger numbers and a longer time period to show an effect if there is one, and our study was not large enough to show smaller effects," she noted.

The study was supported by Monash University. The authors have disclosed no relevant financial relationships.

Ann Rheum Dis. Published online February 11, 2014. Abstract

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