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KNEE JOINT REPLACEMENTS  - “Knee Arthroplasty”

A total knee replacement is really the replacement of the damaged cartilage with artificial surfaces, thus it is not the knee itself that is removed.  The surgeon does not “cut out” the whole knee, he only shaves thin layers of the sick bone away (like peeling an orange) to replace it with the artificial parts.

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The removed damaged cartilage is replaced with a metal alloy on the femur and a metal tray and plastic spacer on the tibia. This creates a new, smooth cushion surface which allows smooth gliding and a pain free, functional joint.  Most patients believe that large pieces of bone are removed from each of the bone ends, when it is actually only a thin layer of bone which is removed by making use of special instruments (jigs).

Knee joint components
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There are various designs of implants available, there is  no consensus as to if and which design is better than the other.  Your orthopaedic specialist will decide which design is best for you based on: your age, your weight, your activity level, the strength of your bones and the shape and condition of your joint.
 
Prostheses can be cemented or un-cemented, depending on the individual patient.  Each prosthesis is made up of three main parts.
 
The femoral component (top part) replaces the bottom surface of the upper bone (the femur) and the groove where the patella fits into.  The femoral component is made of metal. The metal parts of the implant are manufactured from Cobalt-chrome, Titanium or Tantalum.  The articulating parts are made of High Molecular Weight Polyethylene.
 
The tibial component (bottom part) replaces the top surface of the lower bone, the tibia. The tibial component is usually made of two parts: a metal tray that is attached directly to the bone, and a plastic spacer that provides the slick surface. The plastic used is so tough and slick that you could ice skate on a sheet of it without damaging the material much.
 
A cemented prosthesis is held in place by a type of epoxy cement that attaches the metal to the bone. An un-cemented prosthesis has a fine mesh of holes on the surface that allows bone to grow into the mesh and attach the prosthesis to the bone. 

GRAPHIC IMAGES

KNEE JOINT REPLACEMENT

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