While joint arthroplasty improves the functional ability of persons with severe knee osteoarthritis (OA), the long-term effects of surgical intervention on body mass have not been evaluated. The objective of this study was to determine if a reduction in body mass index (BMI) was present following unilateral total knee arthroplasty (TKA) compared to an age-matched healthy control group who did not have surgery.
One hundred and six adults with unilateral, end-stage knee OA and thirty-one persons without knee pain participated in the prospective longitudinal study. Subjects with OA underwent primary unilateral TKA and received post-operative out-patient physical therapy. Height, weight, quadriceps strength and self-perceived functional ability were measured at baseline and at a 2-year follow-up.
There was a significant interaction effect between body mass over time and subject group (P=0.017). BMI showed a significant increase over 2 years for the surgical group (P<0.001), but not for the control group (P=0.842). Sixty-six percent of the persons in the surgical group gained weight over the 2 years with an average weight gain of 6.4 kg, or 14 pounds, 2 years after their initial physical therapy visit. Educational level, marital status, income level and activity level prior to surgery were not related to post-surgical weight gain.
The majority of subjects gain weight after surgery and this cannot be attributed to the effects of aging. Weight gain after TKA should be treated as an independent concern and management of orthopedic impairments will not result in weight loss. Post-operative care should include access to nutrition or weight management professionals in addition to medical and physical therapy services.