Mo. Rev. Stat. § 287.195: Claims for hernia, proof required.

In all claims for compensation for hernia resulting from injury arising out of and in the course of the employment, it must be definitely proved to the satisfaction of the division or the commission:

(1) That there was an accident or unusual strain resulting in hernia;

(2) That the hernia did not exist prior to the accident or unusual strain resulting in the injury for which compensation is claimed.