Passive knee kinematics before and after total knee arthroplasty: are we correcting pathologic motion?

The change in coronal plane deformity throughout a range of flexion before and after total knee arthroplasty (TKA) has not been reported. Unlike most alignment assessments traditionally reporting coronal plane alignment in a standing position under static conditions, this study reports deformity throughout the flexion arc before and after deformity correction. One hundred fifty-two TKA patients using the anteroposterior axis for femoral component rotation and computer navigation techniques were included in the study. Deformity before TKA ranged from 17.5 degrees varus (deformity apex away from the midline) to 20.5 degrees valgus (deformity apex toward the midline) in full extension. Before TKA, deformity was not constant through an arc of motion and significantly decreased with flexion of 60 degrees and more (P < .01). The deformity after performing a TKA was not different (P = .478) throughout the flexion arc. The data determined that deformity is not constant throughout flexion in osteoarthritic knees preoperatively and that deformity throughout flexion can be corrected with the use of conventional alignment techniques during TKA.