Mo. Rev. Stat. § 87.255
Any amounts which may be paid or payable by the city under the provisions of chapter 287 to a member or to the dependents of a member on account of any disability or death shall be offset against and payable in lieu of any benefits payable out of funds provided by the city under the provisions of sections 87.120 to 87.370 on account of the same disability or death. In case the present value of the total commuted benefits under chapter 287 is less than the reserve on the benefits otherwise payable from funds provided by the city under sections 87.120 to 87.370, then the present value of the commuted payments shall be deducted from the reserve and such benefits as may be provided by the reserve so reduced shall be payable under the provisions of sections 87.120 to 87.370.
§ 87.255, RSMo