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Painful Total Knee Arthroplasty: Component Misplacement

- Discussion:
    - malposition of the joint line:
    - varus tibial component positioning
            - AP and lateral mechanical axias views can often identify subtle malalignment
    - flexion of femoral component:
            - will result in loss of full extension;
    - mechanical axis malalignment:
            - the mechanical axis (from the center of femoral head to center of knee, and from the center of  the knee to the center of the ankle should coincide with weight bearing axis);
    - rotational malalignment:
            - either the tibial or femoral component (or both) may be rotationally malaligned;
            - rotational mal-alignment may cause patellar dislocation and problems with foot progression angle;
    - translation malposition:
            - femoral component may be translated medially which will lead to patellar subluxation;
            - tibial component may be translated medially (causing pes bursitis) or may be translated laterally (causing a popliteal tendonitis);
    - patella in TKR:
            - excessive thickness of the reconstructed patella;
            - normal thickness is 26 mm in males and 24 mm in females;
            - may limit flexion;
            - subluxation of patella:
                       - internal rotation of the tibial or femoral component;
                       - medialization of the femoral component;
                       - lateralization of the patella