Being fat increases the risk of primary joint replacement in osteoarthritis

A study published in BioMed Central's open access journal, Arthritis Research & Therapy , found that increased waist circumference and body mass index (BMI) were associated with the risk of both knee and hip joint replacement.

Total joint replacement is an effective treatment for severe knee and hip OA, and obesity is recognized as being the most important modifiable risk factor for OA. BMI is the most commonly used measurement of obesity but does not account for the pattern of fat distribution, and cannot discriminate between adipose and non-adipose tissue.

A research team headed by Flavia Cicuttini of the Monash University, Melbourne, Australia, conducted a prospective cohort study in 32,023 healthy volunteers to examine the relationship between different adiposity measures and the risk of subsequent primary knee and hip joint replacement. BMI, waist circumference and waist-to-hip ratios were measured, and fat mass and percentage fat were estimated.

The study determined that there was a 3 to 4-fold increased risk of primary joint replacement associated with body weight, BMI, fat mass and percentage fat. Waist circumference and waist-to-hip ratio were also associated with an increased risk, suggesting that both biomechanical and metabolic mechanisms associated with adiposity contribute to the risk of joint replacement. The group also showed that fat mass and percentage fat were associated with an increased risk of primary knee and hip joint replacement even 10 to 15 years after their measurement.

According to Cicuttini "Adipose mass contributes to increased joint loading, which may increase the risk of OA progression and subsequent joint replacement for severe end-stage OA. Metabolic factors are also likely to be important since waist circumference and waist-to-hip ratio are known risk factors for metabolic syndrome". She continues, "Adipose tissue is now considered an endocrine organ, releasing a multitude of factors, including cytokines which have been implicated in cartilage destruction".

The authors conclude, "The obesity epidemic occurring in developed countries is likely to have a significant impact on the future demands for knee and hip replacements for OA and understanding the mechanism of action will be important in effective prevention of OA".