Kneeling at high knee flexion angles after total knee arthroplasty does not effect patellofemoral joint contact area and pressure

Thay Q Lee

Orthopaedic Biomechanics Laboratory

VA Healthcare System, Long Beach, California

Department of Orthopaedic Surgery, University of California, Irvine

Introduction: Little is known about the biomechanical effects of kneeling following total knee arthroplasty (TKA).  The objective of this study was to examine the effects of kneeling on patellofemoral (PFJ) joint contact areas and pressures, femoral knee joint reactive force, and patellar kinematics following TKA. 

Materials and Methods: TKA was performed on eight fresh-frozen cadaveric knees using Encore total knee system.  To simulate kneeling, a custom knee testing system that permit physiologic quadriceps loading was used.  All knees were tested at knee flexion angles (KFA) of 90, 105, 120, and 135 degrees and with kneeling force of 0, 50%, and 100% mean body weight.  PFJ contact areas and pressures, femoral knee joint reactive force and patellar kinematics was assessed.

Results: PFJ contact area and pressure increased with kneeling at each KFA except 135º (p<0.05).  At 135º of KFA, double stance kneeling (50% MBW) had no statistically significant effect on PFJ contact area or contact pressures.  Net femoral knee joint reactive force increases with kneeling at all KFA (p=0.0018).  The compressive component of this force increased with kneeling across all KFA (p=0.00018), while the lateral component of this force only increased with kneeling at 135º (p<0.05), and the anteroposterior component of this force experienced changes across all KFA (p<0.05).  Overall, kneeling had minimal changes on patellar tilt, with statistically significant changes in patellar tilt only seen with kneeling at 120º KFA (p=0.012). 

Conclusion: Kneeling after total knee arthroplasty has minimal effect on PFJ biomechanics at hyperflexion.