Mo. Rev. Stat. § 287.148
1. Within one hundred and twenty days of the date of the injury, the employer shall determine whether the injured worker has sustained an injury that results in a loss of suitable, gainful employment. If the employer can determine that a loss of suitable, gainful employment has occurred, the employer may retain the services of a rehabilitation practitioner or a rehabilitation provider. A written determination of this finding shall be sent to the division of workers' compensation with copies to the employer, insurer, employee and their representatives on forms approved by the division. In the event that a determination cannot be established, within the one hundred and twenty days of the date of injury, due to the extent of the injury, the employer shall, as regulated by the division of workers' compensation, continue to review the status of the injured employee at appropriate intervals to determine his loss of suitable, gainful employment. If a rehabilitation practitioner or provider is retained by the employer, the rehabilitation practitioner or provider shall, within ninety days:
2. The employer may retain a rehabilitation practitioner or provider who shall perform the services stated in subdivisions (1) and (2) of subsection 1 of this section, in the event of an injury of sufficient severity as determined by the treating physician, which interferes with occupational functioning that involves:
(L. 1990 S.B. 751)
Effective 7-01-91