Background/Purpose:  Medical treatment for knee osteoarthritis (KOA) can be limited and risk morbidity. Weight loss reduces the arthritis burden and may preclude aggressive treatment. Bariatric surgery trumps diet/exercise for sustainable weight loss; studies suggest improvement in KOA pain long after surgery. We prospectively evaluate the prevalence of painful KOA in obesity and track the effect of bariatrics on knee pain and function. Our hypothesis is that successful weight loss surgery decreases the need for KOA management.

Methods: We screened patients prior to bariatric surgery, targeting knee pain for ≥1 month and a visual analog scale pain ≥30mm. We excluded those with lupus, inflammatory arthritis, psoriasis, or bilateral total knee replacements. Pre-op assessments included BMI, Radiographic severity by Kellgren-Lawrence (KL) grade, questionnaires for knee pain/function (i.e. Knee Injury and Osteoarthritis Outcome Score), and an inventory of KOA treatment – including visits to musculoskeletal subspecialists, medication (oral/topical/intraarticular) and physical therapy. We reassessed patients at 1, 3, 6 and 12 months post surgery, also calculating percent excess weight loss (%EWL).

Results:  Of 536 patients considering bariatric surgery, we found 308 with knee pain and enrolled 176 (91.5% female; mean BMI 43.6 kg/m²±7, range 32-61; mean age 42 ±11, range 18-73). Radiographic severity was well distributed (KL0-KL4). Higher KL grade and BMI correlated with worse pre-op symptoms (data not shown). Patients with worse baseline KL scores visited specialists more often (KL0=33% vs KL3-4=72%, p=0.001) and were more likely to use at least one prescribed treatment (KL0=19% vs KL3-4=57%, p=0.001).

            For the 150 patients who completed bariatric surgery, average knee pain and function improved at each post-operative interval, correlating with %EWL sustained over time (data not shown). We found a marked decrease in treatment used at the intervals, including the 6 month followup. The percent of patients using over the counter analgesics dropped from 87.5% to 47.2% (p<0.0001), visits to specialists fell from 55.7% to 24.7% (p<0.0001), and patients needing the various prescribed treatments decreased from 40.3% to 12.4% (p<0.0001).

            While the attenuated need for KOA treatment trended with %EWL, those with post-op BMI >40 had an increased need for knee specialists – up from 33.3% to 71.4% (post-op month 1 to 12) with a pre-op baseline 53.8%. Conversely, specialist visits for patients with a BMI <40 only rose from 26.8% to 28.6% with a pre-op baseline of 58.6%. Prescription KOA treatment in the post-op BMI>40 group also rose from 11.1% to 43% (post-op month 1 to 12) from pre-op baseline 38.7%, while those patients remaining under a BMI of 40 saw their use of prescription KOA treatment fall from 17.1% to 14.3% with pre-op baseline 42.9%.  

Conclusion: The improvement in KOA symptoms from bariatric weight loss is reflected by a significantly decreased need for treatment. This reduction is sustained over time except in the patients whose BMI remains above 40.  While radiographic severity correlates with patients’ treatment patterns at baseline, it does not appear to limit their ability to decrease knee treatment with successful weight loss surgery.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/reduction-of-treatment-needed-for-knee-osteoarthritis-after-bariatric-surgery/