Impact of Prior Bariatric Surgery Versus Immediate Total Knee Arthroplasty on Knee Function Among Patients Who Have Severe Obesity and Advanced Knee Osteoarthritis: The SWIFT Trial.

BACKGROUND

Severe obesity and its association with advanced knee osteoarthritis (OA) are established risk factors for surgical complications and associated costs of total knee arthroplasty (TKA). This clinical trial examines the functional knee outcomes of severely obese patients who have severe knee OA undergoing bariatric surgery versus immediate TKA and examines the impact of surgical weight loss on the pursuit of TKA.

METHODS

The Surgical Weight-loss to improve Functional status Trajectories trial following total knee arthroplasty was a multicenter, prospective trial examining outcomes of weight loss surgery and TKA in patients who have severe obesity (body mass index ≥ 40 or greater than 35 who have comorbidities) and symptomatic Kellgren-Lawrence grades 3 or 4 radiographic knee OA. Study patients were recruited prospectively from November 2015 to October 2024 and divided into two groups: the bariatric arm (patients undergoing bariatric surgery) and the TKA arm (patients undergoing TKA). Each study arm underwent a comprehensive battery of knee functional assessments at baseline, six, 12, and 24 months, as well as reevaluations in the bariatric surgery arm to assess the need for delaying or proceeding with TKA at 12 and 24 months. There were 232 study subjects who completed surgery and knee evaluation (n = 159: immediate TKA versus n = 73: bariatric surgery). The study groups had comparable degrees of knee disability at study initiation.

RESULTS

Longitudinal functional analysis demonstrated major improvement extending to two years in patient-reported outcomes and performance-based functional assessments in both study arms, with a slight superiority in the TKA arm. Total weight loss % was higher in bariatric surgery patients (28.7%, P < 0.0001). Bariatric surgery resulted in 45 and 36% delays in TKA at 12 and 24 months, respectively, due to improved knee status.

CONCLUSIONS

Knee function and mobility improved significantly in both study arms, with superiority in the Knee Injury and Osteoarthritis Outcome and Western Ontario and McMaster Universities Osteoarthritis Index scores in the TKA group. Improved knee function with surgical weight loss can be associated with up to a 2-year delay in the need for TKA.