Abstract: BACKGROUND: At present, postoperative timing or subjective criteria by clinicians are commonly employed to determine the return-to-sport timing for patients undergoing anterior cruciate ligament reconstruction. Unfortunately, these criteria do not adequately consider the biomechanical deficits in patients following anterior cruciate ligament reconstruction.
OBJECTIVE: To explore the lower extremity kinematic and kinetic characteristics of athletes after anterior cruciate ligament reconstruction during bilateral vertical jumping.
METHODS: Twenty athletes undergoing anterior cruciate ligament reconstruction and twenty healthy athletes, aged 20-24 years, were recruited in Wuhan Sports University from December 2021 to December 2022. All the 40 subjects underwent a bilateral vertical jumping test. The kinematic and dynamic characteristics of the lower limbs at propulsion phase, initial landing time and peak vertical ground reaction force moment.
RESULTS AND CONCLUSION: At the initial landing time, the athletes undergoing anterior cruciate ligament reconstruction showed higher hip flexion angle (P=0.031) and lower ankle plantar flexion angle (P=0.018) on the operated side compared with the healthy athletes. At the peak vertical ground reaction force moment, the athletes undergoing anterior cruciate ligament reconstruction had higher hip flexion angle (P=0.016), lower hip abduction angle (P=0.019), lower knee flexion angle (P=0.025), higher knee external rotation angle (P=0.030), and higher ankle external rotation angle (P=0.042) on the operated side compared with the healthy athletes. At the peak vertical ground reaction force moment, the athletes undergoing anterior cruciate ligament reconstruction showed lower knee extension moment (P=0.036), lower knee internal rotation moment (P=0.016), lower hip abduction moment (P=0.004), higher hip extension moment (P=0.040), and higher hip external rotation moment (P=0.005) on the operated side compared with the healthy athletes. To conclude, the athletes undergoing anterior cruciate ligament reconstruction exhibit a stiff landing pattern, in which the knee load on the operated side tends to shift to the hip joint, and show inadequate control of lower limb rotational stability. Therefore, detection and correction of abnormal biomechanical characteristics should be part of the rehabilitation after anterior cruciate ligament reconstruction.

Key words: anterior cruciate ligament reconstruction, bilateral vertical jump, return to sport, biomechanics, kinematic parameter, kinetic parameter