The present disclosure relates to a device for repairing a patient patella. The device comprises a patellar trial piece and a patellar implant. The patellar trial piece has selectable variable weights to correct mechanical properties of the patient patella. Such mechanical properties to be corrected include a moment of inertia and/or a center of gravity of the patient patella. The patellar implant has embedded weights correspond to the variable weights of the patellar trial piece. In one embodiment, the patellar trial piece has a plurality of variable weights to be inserted into a plurality of holes in the patellar trial piece. The weights are made of different materials. In another embodiment, the patellar trial piece has a rounded top surface and a substantially flat bottom surface with a plurality of pegs. The pegs are selected from pegs with variable weights that are made of different materials.