Research indicates no justification for denying obese patients knee replacements

The research, published online in the journal Annals of the Rheumatic Diseases, shows that clinically obese people (those who have a body mass index (BMI) of above 30 kg/m2) can benefit almost as much as anyone else from the procedure.

Around 55,000 knee replacements are performed each year in England to relieve the pain and disability of knee osteoarthritis. However, in some parts of the country, surgery is offered only to patients who are not clinically obese on the grounds that obesity is itself a risk factor for knee osteoarthritis.

The research team reached its conclusions following a six-year study of two groups of people, all over the age of 45. The first group (325 people) had all had knee replacement surgery and the second group (363 people) had not. At the start and end of the study, all participants completed a validated questionnaire designed to assess their mobility, mental health and wellbeing.

The findings showed that, overall, the mobility of those who had had knee replacement surgery improved over the six years of the study, while it fell in the comparison group. When researchers restricted their analysis to those participants who were obese, improvements in mobility appeared to persist and BMI was not a significant predictor of this improvement.

Professor Cyrus Cooper, Director of the ERC and Professor of Rheumatology at the University of Southampton, said: “The long-term improvement in physical function that we observed in patients who have undergone knee replacement surgery is striking when set against the decline that occurred in the comparison group.

“These benefits extended to those patients who were clinically obese. Our results show that as long as appropriate selection criteria are applied with regard to fitness for surgery, there seems little justification for withholding the operation from patients who are obese.”

Research paper: Long term outcome following total knee arthoplasty: a controlled longitudinal study

Online First Ann Rheum Dis 2008; doi 10.1136/ard.2008.093229]