‘I don’t just refer patients to physical therapy. I instruct the physical therapist about exactly what I want.’ —David T. Felson, MD, MPH
To accurately interpret clinical trial data on medications for knee pain and other therapies, look at meta-analyses’ effect sizes, and watch for red flags that suggest publication bias, said Dr. Felson. Be skeptical of study results that seem too positive, trials that are not randomized and controlled, very small studies or markedly inconsistent results across studies. Trials with null results may never be published, and trials done in developing countries are overwhelmingly and suspiciously positive, he added.
Effect size in a trial is the average improvement in pain on the treatment minus the average improvement in pain while on placebo, divided by the standard deviation, he said. Dr. Felson offered a simple guide to gauge effect sizes of OA treatments: 0.2 to 0.5 is a small treatment effect, 0.5 to 0.8 is a moderate treatment effect, and 0.8 or greater is a large treatment effect. Total knee replacement surgery trials may have effect sizes of closer to 1.5, he said. Due to a strong placebo response in OA trials, look for effect sizes that show the treatment works better than placebo.