Bariatric surgery reduces obesity and pain from osteoarthritis (OA) of the knee, but some patients improve more than others, according to a recent NYU Langone Health study. The findings showed that the youngest patients and patients without prior knee injuries experienced the greatest pain relief after one year, regardless of preoperative body mass index (BMI).

Most Relief for Youngest Patients and Patients Without Prior Knee Injuries

For this one-time telephone study, researchers contacted 120 patients who had undergone laparoscopic adjustable gastric banding (LAGB) at NYU Langone between 2002 and 2015 and asked them to rate their knee pain on a 10-point scale before surgery, 1 year post-surgery, and at the time of the survey. Patients ranged in age from 26 to 69 years, were mostly female and Caucasian, and had an average baseline body mass index (BMI) of 46 kg/m².

Christine Ren-Fielding, MD, professor in the Department of Surgery, chief of the Division of Bariatric Surgery, and co-author of the study, along with senior investigator and rheumatologist Jonathan Samuels, MD, associate professor in the Department of Medicine, reported their findings in the October issue of Seminars in Arthritis and Rheumatism. The authors showed that while the pain relief seen with lap band surgery applied to all patients with osteoarthritic knees, the youngest patients and patients without prior knee injuries experienced the greatest pain relief after one year, regardless of preoperative BMI. Knee pain reduction 1 year post-bariatric surgery was 50 to 60 percent for those in their 40s versus 20 to 30 percent for those in their 60s.

Current clinical guidelines endorse the use of more aggressive sleeve and bypass bariatric surgeries, as well as the less-invasive LAGB, for patients with a BMI of more than 35 kg/m² and at least 1 comorbidity. Although the National Institutes of Health endorses LAGB for patients with lower BMIs, 30 to 35 kg/m², this procedure often is not covered by insurance despite evidence that it can significantly reduce knee pain, notes Dr. Ren-Fielding.

As expected, patients who lost the most weight experienced the greatest knee pain reductions. The improvement was driven not only by the decrease in mechanical load on the knees but also by the decrease in adipose tissue, which affects knee pain by reducing obesity-related inflammation—a finding confirmed by other studies, notes Dr. Samuels.

Examining Markers for Inflammation One Month Post-Surgery

Looking at data from a current cohort, Dr. Ren-Fielding and Dr. Samuels are collaborating on a study led by Manish S. Parikh, MD, associate professor in the Department of Surgery and chief of perioperative services at NYC Health + Hospitals/Bellevue. Examining data from a broader cohort of patients having lap band as well as other types of more-aggressive weight-loss surgeries, the team is investigating the impact of weight loss on underlying biological changes caused by fat tissue and inflammation in the knees. Of particular note are patients who’ve had the most pain relief one month post-bariatric surgery even though weight loss continued.

“Even slight weight loss seems to trigger a decrease in inflammatory markers, which affects how people perceive their knee pain.”—Christine Ren-Fielding, MD

In ongoing studies presented at meetings, researchers noted that it appears that levels of the anti-inflammatory marker known as soluble receptor for advanced glycation end products, or sRAGE—which is often low in obese patients—rose during the first month after surgery. Patients had significantly decreased levels of leptin—an inflammatory mediator found in the blood—at one month as well. The investigators are following up on these findings by studying the effects of sleeve gastrectomy on patients with knee osteoarthritis and by examining the microbiome for other inflammatory markers related to knee pain.

“We now have more insight into how bariatric surgery, including LAGB, may lower inflammatory hormones and chemicals that directly affect knee pain and overall joint health,” says Dr. Ren-Fielding. “It appears that even slight weight loss or caloric restriction has an impact on inflammation.”

Caloric Restriction or Even Slight Weight Loss Can Impact Inflammation

The findings from these studies have important implications for clinicians treating obese patients, Dr. Ren-Fielding adds. For example, LAGB provides another option for patients with a BMI between 30 and 35 kg/m² and mild to moderate knee pain that does not necessarily require orthopedic surgery. “Our findings show that patients don’t need to lose over 100 pounds or undergo surgeries as severe as stapling or resection to improve their knee pain,” says Dr. Ren-Fielding. “Less invasive LAGB can help people lose enough weight to change the inflammatory state of their body.”

Disclosure: Dr. Ren-Fielding: Consultant for Arrow, Inc.

NYU Langone Health is accredited as a Comprehensive Center with Adolescent Qualifications by the Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program (MBSAQIP).