**4. Conclusions**

In conclusion, this paper reviews the recent literature on the innovative design of AFOs, and discusses the development of PAFOs, SAFOs, and AAFOs. PAFOs have attracted attention since the 1980s and scholars have studied continuous designs for the shape and ankle joint styles of AFOs. With the advancement of clinical rehabilitation technology and the in-depth study of human walking gait, the further development of AFOs has been promoted from shape and style to material properties and muscle group responses. SAFOs

and AAFOs have been studied since the early 21st century. Scholars focused on how to reduce the weight of the overall device and increase the portability and wearing experience of the device through different technical methods firstly, and then mainly focus on the role in the field of rehabilitation recently. In addition, it is also important to pay attention to the impact of joint movements other than the ankle so as to provide a new way for clinical rehabilitation training. However, the fundamental research on AFOs is still facing problems such as most experiments on AFOs focusing on the motion angle of the ankle joint, the moment of plantarflexion, and dorsiflexion while the muscle state and in-depth physiological indicators are rarely assessed accurately. Some studies have carried out experiments on the combination of AFOs, botulinum toxin, and FES while most of them are mechanical combinations, and the discussions on the mechanism are rare. In order to achieve smooth and labor-saving walking assistance, it is urgen<sup>t</sup> to focus on breakthroughs in the AFOs elastic drive design and human-in-the-loop assist control technology to carry out theoretical research on the integration of human–computer interaction and physics– physiology integration theory. In addition to studying detailed materials and mechanical properties, innovative AFOs also need to be combined with other clinical rehabilitation methods to provide new ideas and methods for patient rehabilitation.

**Author Contributions:** Conceptualization, C.Z. and X.Y.; Data curation and Formal analysis, Z.Y. and C.Z.; Funding acquisition, C.Z.; Investigation, Z.Y., K.L. and C.Z.; Methodology, Z.Y. and C.Z. Resources, C.Z. and X.Y.; Writing—original draft, Z.Y. and C.Z.; Writing—review and editing, C.Z., Z.Y., K.L. and X.Y. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was supported by Zhejiang Provincial Natural Science Foundation of China under Grant No. LY22H180006, No. LY21E050020.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** The authors would like to thank the related researchers in this area. We also would like to thank Heng Liao, Heyuan Wang, Xuqing Dai, Hangqin Ni, and Qi Zhou for their kind help.

**Conflicts of Interest:** The authors declare no conflict of interest.
