Causation analysis always should be based on current scientific evidence and the facts of a specific case rather than common opinions or beliefs, eg, the myth that “favoring” one lower extremity often results in injury or illness of the opposite lower limb. Temporal sequence does not prove causation, and in causation analysis one also must consider temporal disparity: Was an injury or exposure likely to cause the condition in question, or is there another, more probable, cause? To conclude that a given cause and effect are etiologically associated with a reasonable degree of medical probability or certainty (ie, more than 50% probability), all three of the following criteria must be met: the cause is medically probably; the effect is medially probably; and the cause and effect probably are etiologically related. That is, causation analysis must be based on an analytical approach and not patient history alone. The medical literature reveals no generally accepted studies that support a causal relationship based on an individual's “favoring” one extremity. Rather, evaluators must base conclusions on scientific evidence and facts of the case at hand rather than relying solely on patient history or false logic such as the post hoc propter hoc fallacy.