In vivo sagittal plane kinematics of the Avon patellofemoral arthroplasty.

Isolated patellofemoral osteoarthritis can be treated with patellofemoral arthroplasty (PFA). In contrast to total knee arthroplasty, the effect of PFA on knee joint kinematics is not known. A study was performed to identify the kinematic changes after PFA. The sagittal plane kinematics was examined in 12 patients who had undergone Avon PFA. An established fluoroscopic method was used to examine the patellar tendon angle (PTA)/knee flexion relationship during functional activities. No significant difference existed between the kinematics of PFA knees compared with normal, except for a uniform elevation in PTA throughout the range. This increase in PTA in the PFA joint represents a 1.6-mm anterior displacement of the patella. The kinematic profile after PFA is close to normal and suggests that the knee is exhibiting more normal loading characteristics than those of the total knee arthroplasty joint.