A medical force measuring system is provided for measuring a force effective between two prosthesis parts that are connected to one another in articulated manner in a joint prosthesis which includes a ball joint or a partial component thereof. The force measuring system includes a measuring instrument which has a sample joint element with a sample joint surface. The sample joint element is formed in correspondence with a first joint element that forms a part of the ball joint and has a joint surface which is formed in correspondence with the sample joint surface and is moveable into engagement therewith for forming a sample ball joint. The measuring instrument also includes at least one of a measuring device and an indicating device which cooperates with the sample joint element for measuring and/or indicating a force (or a partial component thereof) effective on the sample joint surface.
