Background/Purpose: Obesity is a modifiable risk factor of knee osteoarthritis (KOA) . While medical treatments for KOA can have a limited effect, an alternative strategy would target weight loss to reduce the arthritis burden. Supportive of other literature, we recently showed in a retrospective analysis that 51% of patients who underwent LapBand surgery reported complete improvement in KOA pain after 18 months. Therefore we began a prospective study to evaluate the prevalence of knee pain and KOA in the obese population, observe how knee pain is treated, and track how bariatric weight loss affects KOA-related pain and physical function.

Methods: We screened consecutive patients prior to bariatric surgery with the LapBand, sleeve gastrectomy, or gastric bypass. We enrolled patients (age≥21) with knee pain for ≥1 month and a visual analog scale (VAS) pain score ≥30mm, excluding lupus, inflammatory arthritis, or psoriasis. Treatment history for knee pain was recorded.  Baseline assessments included validated questionnaires: Western Ontario McMasters Universities Osteoarthritis Index (WOMAC), Assessment of Obesity-Related Comorbidities, and Knee Injury and Osteoarthritis Outcome Score. Those with radiographic KOA by the Kellgren-Lawrence (KL) grading scale >1 will repeat questionnaires post-surgery. 

Results: We evaluated 262 patients, with 136 reporting knee pain and 62 consenting for the study (88.7% female, mean BMI 44.5 kg/m²±8.3, range: 32.0-60.4, and mean age 44 years±10.3, range:22-70). 52% were scheduled for sleeve gastrectomy (mean BMI=43.0 kg/m²), 26% for Lapband (BMI=43.7), and 22% for gastric bypass (BMI=48.8). The mean VAS score was 65.4 (±19.1;range:30-100), WOMAC pain 265.1 (±101.8;range:13-466), WOMAC stiffness 99.1 (±59.2;range:0-187) and WOMAC physical function 917.1 (±427.9;range:0-1589). Baseline radiographs revealed that 96% had evidence of OA (70.6 % KL 2-4 and 25.4% KL1). Despite significant knee pain in this cohort, only 4.8% (3/62) had seen rheumatologists and 17.7% orthopedists — while 55% were treated by primary care and 22.5% had never discussed their knee pain treatment with a physician. Only 37% had taken x-rays previously to evaluate knee pain. Not surprisingly, the ACR OA treatment guidelines were not met in a majority of our cohort: Only 40.3% had been referred for physical therapy, 80.6% tried acetaminophen, 70.9% NSAIDs, 6.4% narcotics, 1.9% SSRI, 12.9% tramadol, 11.2% topical NSAIDs, 16.1% intra-articular steroids, and 3.2% viscosupplementation.

Conclusion: In this early phase of our prospective study of bariatric patients, we found that moderate radiographic KOA is common in obese patients with knee pain. In many cases, pain had been attributed to mechanical load from obesity without proper evaluation or treatment. Few patients were referred to rheumatologists, though would benefit from such evaluation and management. These data indicate that knee OA in obese patients is underdiagnosed and undertreated.  There is a need to educate primary care and bariatric providers that knee pain from OA and other pathology in obese patients should be diagnosed and treated appropriately to maximize their function and quality of life.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/underdiagnosis-and-undertreatment-of-knee-osteoarthritis-in-the-obese-population-the-need-for-physician-education-and-advocacy/