A patient with diabetes and morbid obesity increases the risk of infection following hip and knee replacement, U.S. researchers found. The study, published in the Journal of Bone and Joint Surgery, found diabetes more than doubled the risk of a post-operative joint infection independent of obesity. However, the infection rate was the highest in morbidly obese, diabetic patients, the study said. Dr. Rondi M. Kauffmann, Division of Trauma and Surgical Critical Care at Vanderbilt University Medical Center, in Nashville, and colleagues analyzed 7,181 hip and knee replacements and found that 52 post-operative joint infections occurred within the first year, and that the infection rate increased from a .37 percent in patients with a normal body index to 4.66 percent in the morbidly obese group. Normal body mass index was defined as a body mass index of less than 25, while morbid obesity was defined as more than 40. The authors suggested identifying and/or treating hyperglycemic patients preoperatively, especially if they were obese, would help patients achieve a better outcome by avoiding complications caused by infection. In addition, identifying patients with undiagnosed diabetes would be important for their overall long-term prognosis, the authors said.