COPENHAGEN (Reuters Health) - Orthopedic surgeons are less likely to recommend hip or knee replacement surgery in arthritis patients who are morbidly obese, and their unwillingness to do so is not justified, investigators said here at the European League Against Rheumatism (EULAR) 2009.

"The findings raise the concern that morbid obesity may be used as a screening tool for determining who gets total joint (replacement), despite a lack of evidence showing that morbidly obese patients fare worse," Dr. Said Ibrahim, of the University of Pittsburgh, told Reuters Health.

His group looked at the relationship between body weight and the likelihood of receiving a recommendation for joint replacement in patients with hip or knee arthritis.

The study included about 500 patients with moderate to severe arthritis who had been recruited from two Veterans Administration medical centers.

A standard weight-for-height measure called the body mass index (BMI) was used to divide the patients into weight groups. A BMI of 20 to 25 was considered normal weight, 26 to 29 overweight, 30 to 39 obese, and 40 or higher, morbidly obese. For a 6-foot tall person, a weight of 295 pounds or more would make them morbidly obese.

The results showed that there was a relationship between BMI and the likelihood that an orthopedic surgeon will recommend joint replacement. "The higher the BMI, the more likely the surgeon is to recommend the procedure until the patient crosses the 40 BMI threshold, at which point the likelihood decreases significantly," he said.

Thus, the proportion of patients who received a recommendation for joint replacement was the highest for patients with a BMI between 35 and 40 at 29 percent. Conversely, in subjects with a BMI of 40 or higher, the rate was just 10 percent.

Despite the fact that the surgeons' reluctance to operate on the morbidly obese is not supported by data, Ibrahim said that the study provides an important message to arthritis patients who may benefit from a joint replacement. "The message to patients is to lose weight if they want to be considered for a hip or knee replacement procedure," he said. "And achieving a BMI of 35 to 39 is enough to increase their likelihood of a surgeons' recommendation by about 20 percent."