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18 The Medical Student Notebook Bariatric Times • February 2017 MEDICAL STUDENT This column is written by medical students and is dedicated to reviewing the science behind obesity and bariatric surgery. Notebook The The Effects of Weight Loss and Bariatric Surgery on Knee Osteoarthritis by BRIAN W. YANG Bariatric Times. 2017;14(2):18–20. INTRODUCTION Osteoarthritis is the most common type of joint disorder in the United States, caused by the progressive mechanical wear of cartilage within the joint space. 1 In the knee, this leads to pain, swelling, and decreased function. More than half of adults in the United States diagnosed with knee osteoarthritis will have severe pain that fails nonsurgical treatment and subsequently require a total knee replacement. 2 Risk factors for knee osteoarthritis include advanced age, female gender, repetitive joint injury, joint malalignment, and chronic knee laxity 1 . However, one of the most significant modifiable risk factors for osteoarthritis is obesity. 1,3 In a recent meta-analysis, a five-unit increase in body mass index (BMI) was associated with a 35-percent increased risk of knee osteoarthritis. 4 Increased weight places mechanical increased strain on the knee joint. Data have shown that each pound of weight lost corresponds to a four-fold reduction in force applied to the knee joint. 5 However, mechanisms underlying the connection between weight and osteoarthritis are still varied, including changes in cartilage structure 6 , increased knee joint load, 5,7,8 and knee joint space narrowing. 8,9 When considered in combination, models suggest that persons aged 50 to 84 lose 10 to 25 percent of their remaining quality- adjusted life expectancy due to knee osteoarthritis and/or obesity, with Hispanic and black women showing disproportionately high losses. 10 Furthermore, weight loss has been associated with increased longevity of primary total knee replacements, improved functional scores after total knee replacement, and decreased rates of total knee replacement revision. 1 1–13 Bariatric surgery prior to total knee replacement has also been associated with fewer postoperative complications. 14 Bariatric weight loss surgery has been demonstrated to improve multiple comorbidities associated with obesity, including hypertension, hyperlipidemia, diabetes, and gastroesophageal reflux disease. This article reviews the literature assessing the effects of nonoperative weight loss on knee osteoarthritis and, more specifically, the role that weight loss surgery plays in the improvement of knee osteoarthritis symptoms. NONOPERATIVE WEIGHT LOSS AND ITS EFFECTS ON KNEE OSTEOARTHRITIS Several randomized control trials have evaluated the effects of nonoperative weight loss on the symptoms and effects of knee osteoarthritis. In the randomized Arthritis, Diet, and Activity Promotion Trial (ADAPT), Messier et al studied 316 adults with overweight and obesity with knee osteoarthritis to determine if exercise and dietary weight loss, either in combination or separate, was more effective than a healthy lifestyle control group in improving self-reported knee physical function as measured by the western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Results showed that diet and exercise combined resulted in statistically significant improvements in WOMAC self-reported physical function, distance walked in six minutes, stair-climb time, and WOMAC knee pain scores. 15 However, the diet only group did not show any significant differences when compared to the healthy lifestyle controls and the exercise only group only showed an improvement in distance walked in six minutes. 15 In a more recent study, Christensen et al assessed the effects of weight reduction through a low- energy diet on the symptoms of knee osteoarthritis. Eighty patients with BMIs ranging from 35.9 to 62.6kg/m 2 were randomized into either a low- energy diet group or control diet group, with the WOMAC index used to measure the effects on knee osteoarthritis symptoms. Results showed that a weight reduction of 10 percent improved knee function by 28 percent. Interestingly, reduction in body fat percent was shown to be the best predictor of change in WOMAC index, with every percent of body fat reduced corresponding to a 9.4-percent improvement in WOMAC. 16 This relationship between body fat percentage and knee osteoarthritis relief is corroborated by a randomized control trial by Toda et al. In their study, 22 patients with knee osteoarthritis and a BMI over 26.4kg/m 2 were treated with a low calorie diet, appetite suppressant, and nonsteroidal antiinflammatory drugs (NSAIDs) for six weeks. Data showed a significant correlation between reduction in body fat as well as number of steps per day with decreases in knee osteoarthritis symptoms. 17 Remarkably, weight loss Daniel B. Jones, MD, MS, FASMBS Professor of Surgery, Harvard Medical School Vice Chair, Beth Israel Deaconess Medical Center Boston, Massachusetts ABSTRACT Knee osteoarthritis (OA) is an important cause of morbidity in the United States. One of the most significant risk factors for osteoarthritis is obesity. Both nonoperative weight loss management and weight loss surgeries, including the Roux-en-Y gastric bypass, adjustable gastric band, and others have been demonstrated to improve knee pain, function, and biomechanics in individuals with obesity. This column reviews the current medical literature underlying the roles that nonoperative weight loss and operative weight loss surgery play in the improvement of knee osteoarthritis symptoms. ABSTRACT Knee osteoarthritis, nonoperative weight loss, bariatric surgery, obesity COLUMN EDITOR FEATURED STUDENT Brian W. Yang Medical Student, Harvard Medical School Boston, Massachusetts