Background/Purpose: Obesity is a modifiable risk factor of knee osteoarthritis (KOA). While medical treatments can have limited beneficial effects, an alternative strategy would target weight loss to delay or avoid joint replacement.  Limited retrospective data have shown improvement in KOA pain after bariatric surgery. We initiated a prospective study to evaluate painful KOA in the obese population, and track whether weight loss after bariatric surgery affects KOA-related pain and physical function.

Methods: We screened consecutive patients (N=537) prior to laparoscopic adjustable gastric banding (LAGB), sleeve gastrectomy, or gastric bypass (RYGB). Patients age ≥21 with knee pain for ≥1 month and a visual analog scale pain score ≥30mm were enrolled, excluding lupus, inflammatory arthritis, or psoriasis. Baseline pre-op assessments included x-rays for OA severity by Kellgren-Lawrence (KL) grade, the Knee Injury and Osteoarthritis Outcome Score (KOOS), and the Western Ontario McMasters Universities Osteoarthritis Index (WOMAC) with a Likert scale calculated from the KOOS. Patients are completing the questionnaires and being measured for BMI and % excess weight loss (%EWL) at intervals through 12 months post-op.

Results : In total, 307 patients reported knee pain, and of those, 175 met criteria and consented  (89.7% female, mean BMI 43 kg/m²±7, range: 32-60, mean age 42 ±11, range: 18-73). X-rays were completed on 160 patients: KL0=38, KL1=31, KL2=33, KL3=33, KL4=25.  The mean pre-op KOOS scores were 46 (0=worst, 100=best) for both pain and ADLs, the mean WOMAC pain score was 11 (0=best, 20=worst), and the mean overall WOMAC index was 52 (0=best, 96=worst). Higher KL correlated with symptoms; mean KOOS pain was 54, 49 and 37 for KL0, KL1-2, and KL3-4 (p=0.0006 for KL1-2 vs 3-4), with similar trends across other KOOS and WOMAC scores. Higher BMI also correlated with worse pre-op knee symptoms, as the quartiles with the lowest and highest BMIs (32-38 and 49-61) had mean KOOS pain scores of 48 and 43. Thus far, 117 patients have had surgery (31 RYGB, 64 sleeve, 22 LAGB). Improvement in average KOOS and WOMAC scores over baseline has been observed at all intervals (46, 36, 31 and 7 responses at 1,3,6,12 month visits), with more improvement farther after surgery.  At 6 months post-op, mean KOOS scores improved 29 points for pain, with mean WOMAC pain and index improving by 6 and 22 points.  The %EWL correlated with knee symptoms at each interval and for all followups combined, as the smallest and largest %EWL quartiles (4-29%, 54-92%) showed mean improvements of 18 and 31 points (p=0.03) in KOOS pain – mirrored across KOOS and WOMAC scores. RYGB and sleeve yielded higher %EWL than LAGB (44%, 43% vs. 37%) across all intervals, and greater improvement in mean KOOS and WOMAC scores (e.g. mean KOOS pain increased by 28, 29 and 8). Neither presence nor severity of KOA severity affected knee pain improvement from weight loss. 

Conclusion These data suggest that bariatric surgery improves patients’ KOA pain proportional to weight loss, with durability over time. RYGB and sleeve gastrectomy have more impact on knee symptoms than LAGB.  While patients with worse KL grades report more baseline pain and disability, x-ray severity did not impact the response to weight loss.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/reduction-of-knee-osteoarthritis-symptoms-in-a-cohort-of-bariatric-surgery-patients/