Types of Knee Replacement Devices
In 1947, Shiers, a British Orthopaedic Surgeon, developed the
first true knee joint replacement, which was a simple hinge
joint, pivoting around a central pin. From this early design,
other types of knee prostheses evolved, but they all functioned
in much the same way as a basic hinge joint, with no attempt
made to replicate the complex motion of a normal knee. This was
primarily because there was little knowledge of the way in which
a physiologically normal knee moves.
In most types of total knee replacement devices there are four
parts:
a metal "femoral" component which is placed in the lower end of
the femur
a metal "tibial" component which is placed on the upper end of
the tibia
a plastic "insert" which is placed between the two metal
components and effectively replaces the cartilage
a plastic "patella" component which is sometimes (though not
always) used to resurface the back of the knee cap
Today, there are three main types of knee replacement
devices:
Fixed Bearing Total Knee Systems:
both sides of the knee (the inside or medial compartment and outside or
lateral compartment) are replaced in a single total knee replacement procedure,
and with this type of device the plastic insert is fixed in place.
Mobile Bearing Total Knee Systems:
similar to that above, but with a plastic insert which is able to move
within the joint, allowing more natural and complex knee movements and possibly
creating less wear.
Unicompartmental knee systems:
this type of replacement is used where disease is limited to one compartment
in the knee, and is effectively a “half-knee” replacement
