Abstract:

Objective To investigate the difference of isokinetic angle-specific moment curves between anterior cruciate ligament (ACL)-injured patients with and without patellofemoral cartilage injury (PFCI).Methods A retrospective analysis was performed on patients underwent knee arthroscopy and isokinetic muscle strength testing before surgery from September, 2018 to September, 2019. Seventeen ACL-injured patients with PFCI and 17 ACL-injured patients without PFCI who matched in age, sex and meniscus injury were selected. Before arthroscopy, isometric and isokinetic strength of knee flexion and extension at velocity of 180°/s and 60°/s was tested by isokinetic dynamometer. Normalized torque-angle curves (torque/body mass) were generated in steps of 1° and the differences in angle-specific moment curves between two groups were compared.Results At 180°/s, there was no significant difference in flexion isokinetic torque both healthy side and affected side between two groups (P >0.05); and no difference in extension torque of the healthy side ( P >0.05), however, there was significant difference in extension torque of the affected side at 88° to 90° between two groups ( t > 2.102, P <0.05). At 60°/s, there was significant difference in flexion torque of the healthy side at 62° to 82° between two groups (| t| >2.056, P <0.05), and no significant difference was found in flexion torque of the affected side ( P >0.05), nor in extension torque of both sides between two groups ( P > 0.05). A curve change was found at the beginning of the flexion and extension isokinetic moment curves at the velocity of 180°/s. The isometric knee extension torque was significantly different in the affected side between two groups ( t = 2.858, P < 0.01), and no difference was found in isometric knee flexion torque in the affected side as well as both extension and flexion torques in the healthy side between two groups ( t < 1.905, P > 0.05). Conclusion The lower the isokinetic speed, the more significant the difference of strength is between ACL-injury patients with and without PFCI. High speed exercise is recommended for ACL-injured patients with PFCI.

Key words: anterior cruciate ligament injury, isokinetic angle-specific moment curve, isokinetic muscle test, patellofemoral joint, cartilage injury