LAS VEGAS (FRONTLINE MEDICAL NEWS) – Most of the improvement in knee pain that occurs following bariatric surgery in obese patients with knee osteoarthritis happens in the first month after surgery, well before the bulk of the weight loss takes place, Jonathan Samuels, MD, reported at the World Congress on Osteoarthritis.

This observation suggests that bariatric surgery’s mechanism of benefit in patients with knee osteoarthritis (OA) isn’t simply a matter of reduced mechanical load on the joints caused by a lessened weight burden, Dr. Samuels observed at the World Congress on Osteoarthritis, sponsored by the Osteoarthritis Research Society International.

Indeed, his prospective study of 150 obese patients with comorbid knee OA points to metabolic factors as likely playing a key role.

“Post–bariatric surgery changes in inflammatory biomarkers, especially leptin, may help to explain the symptomatic relief of knee pain – and potential joint preservation,” said Dr. Samuels , a rheumatologist at New York University.

His study, featuring 2 years of follow-up to date, showed that bariatric surgery improved knee OA proportionate to the percentage of excess weight loss achieved. The greatest reduction in knee pain as well as the most profound weight loss occurred in the 35 patients who underwent gastric bypass and the 97 who opted for sleeve gastrectomy; patients who underwent laparoscopic adjustable gastric banding had more modest outcomes on both scores.

The disparate timing of the reductions in excess weight and knee pain was particularly eye catching. With all three forms of bariatric surgery, weight loss continued steadily for roughly the first 12 months. It then plateaued and was generally maintained at the new body mass index for the second 12 months.

In contrast, improvement in knee pain according to the validated Knee Injury and Osteoarthritis Outcome Score ( KOOS ) leveled out after just 1 month post surgery and was then sustained through 23 months. Levels of the inflammatory cytokines and adipokines interleukin-6, interleukin-1 receptor antagonist, and lipopolysaccharides were elevated at baseline but dropped steadily in concert with the reduction in excess body weight during the first 12 months after surgery. In contrast, levels of the anti-inflammatory cytokine sRAGE (soluble receptor for advanced glycation end products) were abnormally low prior to surgery but increased sharply for the first 3 months afterward before leveling off. And levels of serum leptin, which were roughly sevenfold greater than in normal controls at baseline, fell precipitously during the first month after bariatric surgery before plateauing, following the same pattern as the improvement in knee pain.

“This suggests that perhaps leptin is the key mediator in this OA population,” said Dr. Samuels.

Obese patients with knee OA are in a catch-22 situation. Obese individuals are at greatly increased lifetime risk of developing knee OA, and patients with chronic knee pain have a tough time losing weight.

“The treatments that might work with either obesity or knee pain alone often fail when both of these are present,” he observed.

That’s why bariatric surgery is becoming an increasingly popular treatment strategy in these patients. Sleeve gastrectomy, gastric bypass, and laparoscopic adjustable gastric banding are all Food and Drug Administration approved treatments for obesity in the presence of at least one qualifying comorbid condition, and knee OA qualifies.

Dr. Samuels reported having no financial conflicts regarding his study.


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