Patellofemoral kinematics during deep knee flexion after total knee replacement: a computational simulation

Area of Science:

• Biomechanical engineering
• Orthopedic surgery
• Medical simulation

Background:

• Deep knee flexion activities like kneeling and squatting are difficult post-total knee replacement (TKR).
• Understanding patellofemoral kinematics during high flexion is crucial for TKR outcomes.
• Current prostheses claim high flexion capability, but detailed movement analysis is limited.

Purpose of the Study:

• To analyze patellar movement (shifting, tilting, rotation) during deep knee flexion in simulated kneeling and squatting post-TKR.
• To compare patellofemoral kinematics between kneeling and squatting activities after total knee replacement.

Main Methods:

• Utilized a validated computational knee model to simulate TKR biomechanics.
• Analyzed patellar kinematics from full extension to 135° knee flexion.
• Applied distinct forces for kneeling (500 N anterior tibial tubercle force) and squatting (ground reaction force).

Main Results:

• Patellar shifting and rotation patterns were similar during kneeling and squatting.
• Kneeling resulted in greater medial patellar tilt compared to squatting.
• Concentrated force on the tibial tubercle during kneeling induced abrupt patellar tilting.

Conclusions:

• Kneeling is more demanding on the patellofemoral joint after TKR due to higher forces on the tibial tubercle.
• Patients with TKR, especially those who are overweight or require high flexion, should consider avoiding kneeling to minimize polyethylene wear.
• Modifications to trochlear geometry may be necessary to manage abrupt patellar tilting during deep flexion activities.