title: Problems with causality.
authors: E
authors: E
authors: Ernst
mesh_terms: D015670:Acupuncture Therapy; D015984:Causality; D015986:Confounding Factors, Epidemiologic; D006801:Humans; D020370:Osteoarthritis, Knee / Q000628:therapy*; D016032:Randomized Controlled Trials as Topic