The powerful placebo effect in osteoarthritis.

Osteoarthritis (OA) is the most common form of arthritis. Pain and its related function and stiffness are currently the major symptoms and primary outcomes for treatment. However, the treatment in the past has been primarily targeting on the peripheral changes in the joint that has led to suboptimal outcomes. Recently, we find that people with OA respond better to treatment which targets on both peripheral and central pain abnormalities. We also find that placebo per se is very effective for OA. On average 75% pain reduction, 71% functional improvement and 83% stiffness improvement in the treatment of OA are attributable to the placebo/contextual effect. The effect varies between treatments, for example for pain, from 47% with intra-articular corticosteroid injection to 91% with joint lavage. This begs a question on how to improve the overall treatment effect of an OA therapy in clinical practice by enhancing the contextual effect, rather than to separate a specific treatment effect from the contextual effect as we normally do in clinical trials. The enhancement may be achieved by improving contextual factors such as patient-physician interaction or quality of care. Further research on the development of a simple contextual enhancement package that may be delivered by all physicians according to individual needs would be very helpful.