Some TKA Outcomes Improve in Severely Obese Patients Who Lose Weight Before Surgery

    Patients with morbid obesity who lose 20 pounds before total joint arthroplasty (TKA) have a shorter length of stay in the hospital, as well as other improvements in outcome, compared with patients who did not lose weight or who lost less than 20 pounds, according to a study in The Journal of Bone & Joint Surgery.

    The study was designed to assess the benefits of weight loss before TKA in patients with morbid obesity (body mass index 40 kg/m2 or higher), reflecting consistent evidence showing increased rates of adverse outcomes in severely or morbidly obese patients. The researchers reviewed data on 203 morbidly obese patients who underwent TKA between 2011 and 2016 at a single medical center. This group accounted for 13.5% of approximately 1500 patients who underwent TKA during that time.

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    In the months before the procedure:

    • 41% of patients lost at least 5 pounds
    • 29% lost at least 10 pounds
    • 14% lost at least 20 pounds

    The researchers compared the outcomes of each preoperative weight-loss group with those of patients who did not lose weight. Several outcomes were improved in patients who lost 20 pounds or more, but not in those who lost 5 or 10 pounds. After adjusting for other factors, the researchers found that patients who lost at least 20 pounds spent about 1fewer day in the hospital and were 76% less likely to have an extended hospital stay of 4 days or longer. Weight loss of at least 20 pounds was also associated with a 72% reduction in the odds of being discharged from the hospital to a facility.

    Preoperative weight loss was not associated with change in operative time or with postoperative improvement in physical health and function. Hospital length of stay and operative time were significantly increased for patients who gained weight before surgery.

    Most patients who lost 20 pounds or more remained in the morbidly obesity category, the researchers note, and patients displayed “general and expected” postoperative weight gain, with the mean weight almost returning to the preoperative baseline.

    Although morbid obesity is associated with increased surgical risk, it remains unclear whether preoperative weight loss can improve outcomes following TKA. The study authors noted that larger, multicenter center studies are needed to confirm their findings.

    Meanwhile, this study provides orthopaedic surgeons with new evidence that weight loss of 20 pounds or more – even if only temporary – can improve length-of-stay outcomes and reduce costs of TKA in morbidly obese patients.


    Keeney BJ, Austin DC, Jevesevar DS. Preoperative weight loss for morbidly obese patients undergoing total knee arthroplasty: determining the necessary amount. J Bone Joint Surg Am. 2019 Aug 21;101(16):1440-1450. doi: 10.2106/JBJS.18.01136.