Background: Evidence linking increased body weight to osteoarthritis
of the knee and the high prevalence of obesity underscore the importance of
defining the outcome of total knee arthroplasty in obese patients. The purpose
of this study was to compare the clinical and radiographic results of total
knee arthroplasties performed in obese patients with those of total knee
arthroplasties performed in nonobese patients.
Methods: Clinical and radiographic data on seventy-eight total knee
arthroplasties in sixty-eight obese patients were compared with data on a
matched group of nonobese patients. The analysis was also performed after
stratification of the obese group for the degree of obesity. All patients had
the same prosthesis. The clinical data that were analyzed included the Knee
Society objective and functional scores, patellofemoral symptoms, activity
level, and complications.
Results: The percentage of knees with a Knee Society score of =80
points at an average of eighty months was 88% in the obese group, which was
significantly lower than the 99% rate in the nonobese group at the same time.
The morbidly obese subgroup had a significantly higher revision rate than did
the nonobese group (p = 0.02).
Conclusions: The results of the present study suggest that any
degree of obesity, defined as a body mass index of =30, has a negative
effect on the outcome of total knee replacement.
Level of Evidence: Prognostic study, Level II-1
(retrospective study). See Instructions to Authors for a complete description
of levels of evidence.