Background In Denmark the numbers of primary total knee arthroplasty (TKA) operations annually increase. In the year 2000 was performed approximately 2,500 operations and in 2008 was performed more than 7,500 total knee arthroplasty operations, and there appears in all countries to be similar tendency. Meanwhile, the prevalence of overweight and obesity has increased markedly over the last 50 years. Approximately 13% of the Danish population is obese. For several years the association between obesity and knee osteoarthritis (OA) has been recognized, and osteoarthritis is the most frequent indication for total knee arthroplasty(80%).