EACH GAIT CYCLE
• Flexion and extension -70 * swing
20 * stance
• Abduction and adduction 10 *
• internal and external rotation - 10 to 15*
• 67* flexion for swing phase
• 83* flexion for climbing stairs
• 90* flexion for descending stairs
• 93* flexion for rise from chair
NORMAL POST TRANSLATION OF KNEE IN
• Medial condyle = 2mm
• Lateral condyle = 21 mm
• Medial based pivoting of the knee
• In flexion - tibia undergoes internal rotation
• In extension - tibia undergoes ext rotation
• MA is 3 degrees
of valgus from
vertical axis of
• AA is in 6 * of
valgus from MA
•9 degrees of
valgus vertical axis
• The tibial articular surface is in 3* of varus.
• The distal femur is in 9* of valgus
• So in order to get the neutral mechanical axis
in TKR we insert the femoral component in
5-7* of valgus.
• Proximal tibial cut is perpendicular to the
• Posterior condylar axis is 3*
• In order to create a rectangular flexor space
the femoral component should be in 3* ER
JOINT REACTION FORCE
• It’s the force experienced by the trochlea due
to posterior displacement of the patella
• JRF increases with flexion
• Normal ADL it is 2-5 times
• Squatting and 120* flexion 8 times
EVOLUTION OF KNEE PROSTHESIS
• Mold arthroplasty
• Hinged knee implants- they did not account
for the complex knee motion.
• Bi-compartmental prosthesis-
1. Gunston- polycentric knee
ARGUMENTS IN FAVOUR PCL RETAINING
• > range of motion with effective femoral roll-
• restraint to translational displacement
• more symmetrical gait.
• less bone resection
• improved function of the patellofemoral joint
• proprioceptive role of the PCL
PCL substituting design the displacement must
be resisted by the prosthetic articular
Inc stress on the prosthesis
Inc stress transfer to the bone cement
• SYMMETRICAL GAIT more so in stair climbing
• PCL substituting
1. decreased knee flexion
2. tendency to lean forward in a quadriceps-
• Contradicting studies both in favor of and
against PCL retaining.
• The patella to the joint line is less altered with
• Improved patello-femoral joint function
• Patellar clunk syndrome with PCL-S.
ARGUMENTS IN FAVOUR PCL SUBSTITUTION
• PCL is diseased with arthritis and contracture
• Technically surgery is less demanding
• No problems related to a too loose or a too
• Better deformity correction
• No problems with excess femoral rollback
• Less polyethylene wear.
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