Differences in patellofemoral kinematics between weightbearing and non-weightbearing conditions in patients with arthrofibrosis after anterior cruciate ligament reconstruction.

OBJECTIVE

The purpose of this study is to evaluate the difference of patellofemoral kinematics between weightbearing and non-weightbearing conditions in the arthrofibrotic knee after anterior cruciate ligament (ACL) reconstruction.

METHODS

Twenty patients with arthrofibrosis after ACL reconstruction were included in the study. Computed tomography scanner and dual fluoroscopic imaging techniques were used to compare patellofemoral kinematics of the affected knee between weightbearing knee flexion and non-weightbearing knee flexion. In both positions, patellofemoral kinematics in six degrees-of-freedom (6 DOF) were measured respectively.

RESULTS

The patellar lateral tilt angle (p = 0.007) and medial patellar translation (p = 0.043) under the weightbearing condition were significantly decreased compared to the non-weightbearing task between 5° and 15° of knee flexion. The lateral patellar translation during a non-weightbearing task was significantly decreased between 60° and 75° of knee flexion (p = 0.005), and the inferior patellar translation under the weightbearing condition was significantly increased between 45° and 75° of knee flexion (p = 0.040).

CONCLUSION

These results indicate that patellofemoral kinematics during non-weightbearing positions do not sufficiently represent the patellar tracking during functional weightbearing activities. Our findings of this study establish the clinical relevance and significance of assessing the patellofemoral kinematics under the weightbearing condition when evaluating patients with arthrofibrosis after ACL reconstruction.

TRIAL REGISTRATION

Trial registration number: ChiCTR1900025977.