Weight Gain Likely Following Knee Arthroplasty

As if getting a new knee was not traumatic enough, a new study indicates that a significant post-surgery weight gain is likely to follow. Nancy Walsh, staff writer for MedPage Today, reports May 1 that on an adjusted multivariable analysis, recipients of knee arthroplasty were 60% more likely to gain 5% or more of their baseline body weight than were matched controls who did not have the procedure. The weight gain took place over a five-year postoperative period. Daniel L. Riddle, Ph.D., of Virginia Commonwealth University in Richmond, Virginia and his colleagues conducted the study.

Individuals who had a second arthroplasty during the subsequent five years found that the chance of experiencing that “clinically important” weight gain doubled. Riddle and his colleagues analyzed outcome data for 917 patients in the Mayo Clinic arthroplasty registry. They matched them with 237 controls from the population-based Rochester Epidemiology Project. A total of 205 of the 917 Mayo patients had a second lower-limb or hip arthroplasty procedure.

The subjects’ baseline weight was 89.1 kg (196 lbs) in the arthroplasty group and 76.3 kg (168 lbs) in the control group. Two-thirds of the subjects were women. Walsh noted that during the first year after the surgery, 22.1% of patients gained 5% or more of their body weight, compared with 16% of the controls. In the fourth year, 32.3% of the surgery patients had that percentage weight gain, as did 22.8% of the controls.

Prior to conducting their study the researchers reasoned that, “The logical assumption may be that persons who are overweight or obese prior to surgery are more likely to lose weight following surgery. Because there is less pain and improved mobility, the impediments to increased activity and exercise are eased following surgery, and weight loss would logically follow.” Obviously, they were wrong in their assumptions.

Walsh reported that in the five years after the index date, the controls averaged a mean weight loss of 0.35 kg (0.77 lbs.), while those who had just one arthroplasty gained an average of 1.23 kg (2.7 lbs.). Those patients who had a second arthroplasty experienced a mean weight gain of 2.62 kg (5.77 lbs.).