Surgeons are not very good at predicting benefit from knee operations, a new study in the Netherlands finds.

These findings offer one reason these knee operations remain common despite a growing body of evidence suggesting many patients don’t benefit, said to Reuters Dr. Victor van de Graaf, lead author of the study and a researcher at University Medical Centre, Utrecht, in the Netherlands.

Overall, surgeons correctly predicted which patients would benefit from operations only half of the time. And experienced knee surgeons were no better at guessing correctly than other orthopedic surgeons.

Results from the study were published in the British Journal of Sports Medicine.

20 test cases with tears in the meniscus

Researchers created test cases based on actual patients to see whether the surgeons could accurately predict who would benefit the most from knee operations, or least, from surgery or from exercise therapy.

Researchers surveyed 194 surgeons to see whether they would recommend surgery or exercise therapy in 20 test cases with middle-aged patients who had tears in the meniscus, the cartilage that works as a cushion between the shin and thigh bones.

To understand how accurately surgeons could predict patient outcomes, researchers asked a series of questions for each of the 20 patient cases. They asked whether patients should get surgery or physical therapy; what amount of improvement or deterioration would be expected in function after two years; and what level of function patients would have if they went with the treatment surgeons didn’t recommend.

Who would not benefit from the surgery?

Surgeons were more likely to make correct predictions about who would benefit from knee operations or physical therapy, but more likely to be wrong about which patients would not benefit from the treatments.

Among patients who didn’t respond to surgery, only 39% of the surgeons correctly foresaw this outcome. And among patients who didn’t respond to exercise therapy, only 29% of surgeons correctly predicted this outcome.

Read the whole study HERE