Total knee arthroplasty may be associated with weight gain

Patients who undergo knee arthroplasty may be at risk for weight gain in the five years after surgery, according to a new study.

Researchers used data from a Mayo Clinic knee joint registry and a population-based sample of controls from the same region in Minnesota to study whether patients who had total knee arthroplasty (TKA) had a higher risk of clinically important weight gain, defined as at least 5% of baseline body weight, in the first five years postsurgery. The Mayo Clinic registry, which originated in 1971, collects data on follow-up outcomes at two and five years from patients who had TKA at Mayo. The study included patients who had primary TKA from Jan. 1, 1995, to Dec. 31, 2005. Patients who had had bariatric surgery or any cancer besides basal-cell carcinoma two years or less before or up to five years after the index TKA were excluded, as were patients who did not provide informed consent and those who had bilateral TKA on the same day. The study results appeared in the May Arthritis Care & Research.

A total of 1,122 TKAs in 917 patients were included in the study. Most of the patients (64% in both the TKA and control groups) were women. Thirty percent of patients who had TKA experienced clinically important weight gain in the five years after surgery compared with 19.7% of controls (multivariable-adjusted odds ratio, 1.6; 95% CI, 1.2 to 2.2). Patients who underwent at least one other arthroplasty procedure in the follow-up period were even more likely to gain weight than controls (odds ratio, 2.3; 95% CI, 1.6 to 3.2). A multivariable logistic regression model that included only TKA patients found that younger patients and patients who lost more weight in the five years before surgery also had higher risk for clinically important weight gain after surgery. Body mass index at baseline was not related to risk for later weight gain.

The authors acknowledged that one-third of the study patients and almost half of the controls were missing five-year data on weight and that they did not know the reasons for subjects' weight changes. However, they concluded that their study shows an association between TKA and clinically important weight gain soon after the procedure, especially in patients younger than age 70 and in those who lost a greater amount of weight before surgery. These findings are relevant for primary care physicians managing patients post-TKA, the authors said.

“Multidisciplinary weight loss/maintenance interventions particularly directed to those TKA patients who are younger and have lost considerable weight prior to surgery should be considered,” the authors wrote. “Given the challenges of losing or maintaining weight over the long term, research efforts should target this subgroup of patients.”