The present invention relates to variable thickness tibial insert trial. The variable thickness tibial insert trail comprising of at least one proximal plate bearing threads at its post,at least one distal plate having at least one lower resting surface capable of being deployed over implantation site, at least one combination of gear and thread mechanism comprising of at least one driven gear member with threads and at least one driving member. The threads of the driven gear member is being engaged with the threads of the post of the proximal while said driven gear member of said driven gear member with threads is engaged with said distal plate when said driven gear member with thread is actuated by said driving member said proximal plate moves in distal-to-proximal direction or proximal-to-distal direction to provide tibial trial insert which is adjustable from minimum thickness to predetermined thicknesses or vice versa without being removed from implantation site.
