Sample Size
A pain reduction of 1.75 cm on a VAS is recommended as the minimum clinically important difference to be detected in OA trials.33 With 58 participants, the study had 90% power to detect a difference in pain reduction of 1.75 cm between groups, assuming a standard deviation of 2.0 cm and a significance level of 5%. Numbers were increased to 71 participants to allow for dropouts.