## 4 Discussion
### Joint Coordination Analysis  
Our findings revealed that while no significant differences existed in joint coordination between the experimental (EG) and control groups (CG) at T1, the EG demonstrated superior hip-ankle isotropic coordination, stronger proximal hip-knee coordination, and reduced knee-ankle inversion coordination at T3, indicating the positive effect of resistance-enhanced bracing on joint coordination. This improvement was particularly evident in patients with moderate to severe ACL injuries [27], where progressive resistance provided optimal rehabilitation intensity to restore neuromuscular control without compromising healing tissues. The observed transition to more isotropic and proximal movement patterns with reduced inversion coordination suggests improved force transmission and movement synergy, with the resistance brace effectively addressing the coordination deficits typically seen in higher-grade ACL injuries [28]. The significant reduction in knee-ankle inversion coordination points to enhanced gait mechanics and joint stability [29], which are crucial for postoperative rehabilitation, particularly for cases requiring higher rehabilitation intensity due to greater initial impairment [30]. While previous studies have shown that resisted bracing improves knee-specific motor control [31], our study extends these findings by demonstrating comprehensive lower-limb coordination benefits, a critical advancement given that most prior research failed to account for injury severity when assessing coordination outcomes [32]. Importantly, unlike earlier studies that used restrictive rigid braces [33]--which may artificially alter coordination patterns [34] and are particularly unsuitable for patients with severe injuries requiring progressive mobility--our matched-mobility design isolated the specific effects of resistance. This methodological refinement explains why we detected coordination improvements where previous studies using conventional bracing protocols did not [35], particularly in the crucial 2-month postoperative window when rehabilitation intensity needs to be carefully calibrated to injury recovery status. Our findings not only validate the clinical utility of resistance bracing but also highlight its particular value for patients with greater baseline impairment who require graduated, intensity-adjusted rehabilitation approaches.  
In addition, the choice of time point also appears to be particularly important. Previous studies have mostly assessed joint coordination at the T0 time point, the early stage after surgery, when patients are more affected by joint injuries, and it may be difficult to accurately differentiate the effects of the intervention. Instead, we chose to assess joint coordination at T1 and compare the results with those at T3, which provided more convincing data to support the study. At T1, there was no significant difference in joint coordination between the intervention and control groups, suggesting that joint coordination may be affected by both injury and rehabilitation during the initial postoperative rehabilitation phase. In contrast, at T4, after two months of intervention, the experimental group showed a significant improvement in joint coordination, further demonstrating the facilitating effect of the knee brace and its increased resistance on the recovery of joint coordination. Our study reveals the significant impact of knee braces with resistance on joint coordination recovery. Specifically, the experimental group appeared to have better joint coordination within 2 months postoperatively, especially in terms of improvement in isotropic coordination, proximal coordination, and reduction in reverse coordination, which provides strong support for functional rehabilitation after ACL reconstruction. This finding provides a new theoretical basis for the clinical application of knee braces, as well as new perspectives and ideas for future related research.