Knee Replacement Surgery More Costly for Obese Patients


Obesity causes extra stress to be placed on the knees, increasing the risk of osteoarthritis and eventual knee replacement surgery. But obesity can cause another problem as well. Researchers have found that performing knee replacement surgery on an overweight or obese person takes more time and therefore increases hospital expenditures and other resources.

Geoffrey Westrich MD, an adult reconstruction and joint replacement surgeon and co-director of Joint Replacement research at the Hospital for Special Surgery (HSS) in New York, and colleagues retrospectively reviewed data from 454 total knee arthroplasty surgeries (TKA) conducted by one surgeon between 2005 and 2009. They categorized patients into weight classes based on the World Health Organization’s definition of obesity: normal weight (BMI 18.5-24.9), overweight (BMI 25-29.9), obesity class I (BMI 30-34.9), obesity class II (BMI 35 to 39.9) and obesity class III (BMI 40 or greater).

Seventy percent of the study patients were classified as overweight or obese.

Read: Obesity Causing 1 in 4 Americans Arthritis

The team then correlated weight with five factors including anesthesia induction time, tourniquet time (the time beginning with incision and ending with cementing of the bone), time spent surgically closing the knee after the procedure, total surgery time, and total amount of time spent in the operating room.


Dr. Westrich found that as BMI increased, so did the time it took to perform all parts of the surgery. Class III obese patients spent two hours and 24 minutes in the OR, compared to only two hours for normal weight patients, an increase of 20%.

“If you have a 20 percent greater utilization for someone who is obese and if you multiply that by five or six knee replacements over the course of a day, at the end of the day the operating room staff could be finishing up two hours later,” says Dr. Westrich. “In many cases, the hospital has to pay the staff overtime, which greatly increases hospital expenditures.”

Read: The Impact of Weight Loss on Osteoarthritis of the Knee

“Hospitals should not only take into account the type of surgery and its complexity, but also the patient’s body mass index when appropriately allocating OR time,” he concluded.

According to background information, the number of TKA’s performed in the United States between 2000 and 2004 increased by 53%. This number is expected to continue to rise as obesity trends continue.

Source Reference: The Increased Use of Operating Room Time in Obese Patients during Primary Total Knee Arthroplasty, Paper 595 presented Friday, February 18 at the American Academy of Orthopaedic Surgeons annual meeting, held in San Diego, CA.