Abstract: BACKGROUND: The re-injury rate of the anterior cruciate ligament continues to be high and the unclear relationship between neuromuscular function and biomechanical risk factors may be one of the reasons for poor injury prevention and rehabilitation.
OBJECTIVE: To evaluate the biomechanics and neuromuscular function characteristics of the knee joint during landing movements after anterior cruciate ligament reconstruction, and to further explore the effects of muscle strength, proprioception, and dynamic postural control on the risk indicators of anterior cruciate ligament injury during landing maneuver.
METHODS: Twenty-six male anterior cruciate ligament reconstruction patients and 26 healthy control males at the age of 18-35 years were recruited and randomized to undergo joint kinesthesia test, Y-balance test, and isometric muscle strength tests. Kinematic and kinetic data of the knee joints during single-legged jump landing tasks were collected using an infrared motion capture system and force plates.
RESULTS AND CONCLUSION: (1) Compared with the healthy control group, patients after anterior cruciate ligament reconstruction demonstrated higher knee valgus angle (P=0.021), lower hamstring muscle strength (P < 0.001), lower quadriceps muscle strength (P < 0.001) and Y-balance anterior reach distance 
(P < 0.001), and worse knee flexion kinesthesia (P < 0.001) and extension kinesthesia (P=0.001). (2) The predictor variables of knee extension moment were quadriceps strength and knee flexion kinesthesia (R2=0.298, P=0.007). The predictor variable of knee varus and valgus angle was hamstring strength (R2=0.117, P=0.048). The predictor variable of knee internal and external rotation angle was the hamstring-to-quadriceps peak torque ratio (R2=0.134, P =0.037). (3) The results showed that after anterior cruciate ligament reconstruction, patients still had abnormal biomechanical action patterns and neuromuscular function defects in the frontal plane of the knee joint, and elevating the muscle strength of the hamstrings, avoiding excessive quadriceps muscle strength and enhancing the proprioception of the knee joint were helpful to improve the biomechanical patterns of the sagittal plane, frontal plane and horizontal plane of the knee joint and reduce the risk of anterior cruciate ligament injury during landing maneuvers.

Key words: anterior cruciate ligament reconstruction, neuromuscular function, muscle strength, proprioception, dynamic postural control, re-injury risk, engineered tissue construction