An adjustable tibial trial insert includes an upper plate having an upper
articular surface and a lower plate. A height-adjustment mechanism of the
insert is coupled to and positioned generally between the upper plate and
the lower plate and is configured to move between a closed position where
the upper and lower plates are adjacent each other and an opened position
where the upper and lower plates are spaced-apart from each other in
order to adjust a height or thickness of the insert.