The purpose is to explore the effects of Exercise rehabilitation (ER) on bone mineral density (BMD) of the knee, muscle strength (MS), and physical function (PF) after ACL rupture. Finally, A total of 58 patients were randomized into 2 groups (Control Group [CON]: conventional treatment, male ​= ​16, female ​= ​13, age ​= ​[31.63 ​± ​8.01] years; Exercise rehabilitation group [ER]: 6-week ER on CON basis, male ​= ​17, female ​= ​12, age ​= ​[31.26 ​± ​7.07] years). At baseline and 6 weeks, the knee BMD was measured using DEXA, MS and PF measures were recorded by isokinetic strength test, IKDC, Lysholm, and VAS score. T-tests, analysis of variance (ANOVA), and Mann-Whitney tests were used for comparisons. The BMD outcomes: after a 6-week period, the BMD of the CON ([1.47 ​± ​0.24] g·cm⁻²) was significantly lower than that of the ER ([1.65 ​± ​0.37] g·cm⁻²) at lateral condyle of femur (LCF) (p ​= ​0.041). MS outcomes: at 6 weeks, the relative peak torque (RPT) of the quadriceps and hamstrings during concentric contractions in ER group were significantly higher than that in CON group (p ​< ​0.001, p ​= ​0.017). Similarly, during eccentric contractions in ER group, the RPT of the quadriceps and the H/Q ratio revealed significant variations from the CON group (p ​= ​0.033, p ​= ​0.043). PF outcomes: the IKDC, Lysholm, and VAS scores of the ER group were significantly improved compared to the CON group (p ​< ​0.001, p ​< ​0.001, p ​= ​0.002). The conclusion is that 6 weeks of ER intervention for patients with ACL rupture can effectively delay the decline of BMD in the LCF of the knee joint, and enhance the restoration of MS and PF. This provides guidance for clinical rehabilitation.

Gait asymmetries after anterior cruciate ligament reconstruction (ACLR) may lead to radiographic knee osteoarthritis (OA) and secondary injury. This study aimed to investigate three-dimensional (3D) lower limb joint kinetics using a multi-body dynamic analysis method based on a subject-specific musculoskeletal model during level walking 2 years after ACLR. A total of 23 patients (2 females and 21 males) 2 years after ACLR were selected and underwent gait testing. 3D motion joint reaction forces and the internal moments of the hip, knee, and ankle joints for the stance phase of each gait cycle were calculated by a musculoskeletal multibody dynamics model. In the hip and ankle joints, the peak of the first anteroposterior forces on the affected side were significantly smaller compared to the non-affected side (both p ​= ​0.04). The abduction (peak2: p ​= ​0.01) and the internal rotation moment (peak1: p ​= ​0.02; peak2: p ​= ​0.01) of the affected knee were significantly smaller than the non-affected side, but both of them did not reach the Minimal clinically important difference. The external rotation moment of the affected ankle moments was greater than the affected side (p ​< ​0.01). Two years after ACLR, there was no clinically significant kinetic abnormality in the affected knee joint, the kinetics of the hip and ankle joint were still abnormal, which may lead to the development of OA and secondary injury. Gait retraining should be used to improve the kinetics of the hip, knee, and ankle after ACLR.