Introduction

Conundrums in musculoskeletal research are common. Halliday and colleagues1 demonstrated similar outcomes for patients with chronic low back pain who received two seemingly different interventions: (1) a McKenzie approach and (2) motor control exercises. Chmielewski and associates2 reported similar knee function and psychosocial status scores in those who received either low intensity or high intensity plyometric exercise programmes. Finally, van Beijsterveildt et al found no differences in the prevention of injuries among amateur footballers when usual care was compared against an exercise strategy that consisted of core stability, eccentric training of thigh muscles, proprioceptive training, dynamic stabilisation and plyometrics exercises.3 These findings beg the question: Why do we see similar outcomes in randomised trials, which compare treatment strategies that are ostensibly different? Our goal is to provide explanations beyond the obvious answers—such as treatments that have similarly effective or ineffective causal mechanisms or failing to account for patient heterogeneity in trial design and consequent insufficient statistical power to detect differences. In this editorial, we present the reader with four additional yet plausible explanations for why trials report similar outcomes.