A method of implanting a joint prosthesis assembly for joint arthroplasty using a coupling mechanism is disclosed. The method includes exposing a joint of a patient, resecting a portion of the joint, inserting a second prosthesis of the joint prosthesis assembly into a medullary canal, and inserting a first prosthesis of the joint prosthesis assembly from a lateral side of the joint. The joint prosthesis assembly includes a magnet. The magnet is configured to lock the first prosthesis of the joint prosthesis assembly to the second prosthesis of the joint prosthesis assembly. The first prosthesis of the joint prosthesis assembly includes a recess. The second prosthesis of the joint prosthesis assembly includes a protrusion. The recess is configured to house the protrusion. Alternatively, the first prosthesis and the second prosthesis may be assembled in a direct line using the magnet for secure coupling of the components.