Clinical equipoise and personal equipoise: two necessary ingredients for reducing bias in manual therapy trials.

Clinical and personal equipoise exists when a clinician has no good basis for a choice between two or more care options or when one is truly uncertain about the overall benefit or harm offered by the treatment to his/her patient. For most manual therapy trials, equipoise does not likely exist. Because of the nature of the intervention a lack of equipoise can lead to bias and may account for a portion of the 'effect' that has traditionally been assigned to the intervention. Although there are methodological mechanisms to reduce the risk of bias associated with a lack of equipoise, most of the manual therapy trials to date are likely guilty of this form of bias.