Research articleRelationships between body mass indices and surgical replacements of knee and hip joints
Introduction
O steoarthritis (OA) is the most common form of arthritis, with about 5% of the U.S. population having hip or knee OA. Among adults aged ≥62 years, the prevalence of knee OA has been estimated at 9.5%.1 OA is severely debilitating in many cases and frequently leads to joint replacement surgery. More than 70% of total hip and knee joint replacements are due to OA.1
Body mass index (BMI), a relative measure of weight, has been associated with OA of the knee in a number of cohort,2, 3, 4, 5 case-control,6, 7 and cross-sectional studies,8, 9, 10 but the data relating obesity and hip OA are inconsistent. Although a few studies have found an association between obesity and hip OA,11, 12, 13 other studies have found no association.14, 15 The effect of BMI on OA is a rising concern as obesity rates in the United States continue to climb. According to 1999 national statistics, 61% of the U.S. adult population is either overweight (BMI 25 kg/m2 to 29.9 kg/m2) or obese (BMI >30 kg/m2).16
We hypothesized that those overweight and obese are more likely to develop generalized OA17, 18, 19 that leads to OA of both the hip and knee joints, which will be associated with elevated risks for joint replacement surgeries. It was also hypothesized that obesity is a risk for partial hip replacements and revisions of the hip and knee joint replacement surgeries, although we are unaware of any previous studies of those outcomes. A large case-control study was designed to estimate the risk of increasing BMI on knee and hip replacement surgeries.
Section snippets
Methods
The University of Utah's Institutional Review Board approved this study.
Results
The relationship between increasing BMI and total hip replacement surgery appears stronger in males than females (see Table 3). However, there is a fairly consistent relationship in both genders. Statistical significance was achieved in the BMI groups 30.00 to 32.49 kg/m2 and above in males and in the BMI groups 27.50 to 29.99 kg/m2 and above in females. The chi-square linear test for trend in both males and females was highly significant (p<0.0001). The interaction term from the regression
Discussion
The relationship between increasing BMI and total hip replacement surgeries in this study is strong in contrast with some prior reports.11, 12, 13, 14, 15 This study confirmed other findings of strong associations for knee replacement surgery.2, 3, 4, 5, 6, 7, 8, 9, 10 The compelling OR concerning the total knee procedure lends greater evidence that being overweight, not just obese, is a risk factor for developing OA. There was also a relationship between increasing BMI and hip revision and
Acknowledgements
This study was partially supported by a grant from the Centers for Disease Control and Prevention/National Institute for Occupational Safety and Health (Training Grant T42/CCT810426-06-1). This study was also partially funded by the Prostate Lung Colorectal and Ovarian Cancer Screening Trial, University of Utah (contract N01-CN25524).
We are grateful for the help of Dr. Brent James and Abe Lindemen from Intermountain Health Care for helping obtain the data. We are also grateful to Dr. Saundra S.
References (40)
- et al.
Obesity and osteoarthritis of the kneeevidence from the National Health and Nutrition Examination Survey (NHANES I)
Semin Arthritis Rheum
(1990) - et al.
Obesity, overweight and patterns of osteoarthritisthe Ulm osteoarthritis study
J Clin Epidemiol
(2000) - et al.
Stimulation by human interleukin 1 of cartilage breakdown and production of collagenase and proteoglycanase by human chondrocytes but not by human osteoblasts in vitro
Biochim Biophys Acta
(1984) - et al.
Body mass index in young men and the risk of subsequent knee and hip osteoarthritis
Am J Med
(1999) - et al.
Self-reported weight and heightimplications for obesity research
Am J Prev Med
(2001) Weight and osteoarthritis
Am J Clin Nutr
(1996)- et al.
Obesity and knee osteoarthritisthe Framingham Study
Ann Intern Med
(1988) - et al.
Incidence and progression of osteoarthritis in women with unilateral knee disease in the general populationthe effect of obesity
Ann Rheum Dis
(1994) - et al.
Incidence and risk factors for radiographic knee osteoarthritis in middle-aged womenthe Chingford Study
Arthritis Rheum
(1999) - et al.
Overweight, gender and knee osteoarthritis
Int J Obes
(1996)