Background: Anterior cruciate ligament reconstruction (ACLR) causes a reduction in the balance of the lower extremities. Static and dynamic balance were evaluated separately to confirm the decrease in balance in patients underwent ACLR. The commonly used methods include the Biodex Balance System (BBS) for static balance and the Y balance test (YBT) for dynamic balance. No study has evaluated whether the static and dynamic balance of the involved side recovers as much as the uninvolved side one year after ACLR.
Objects: The purpose of this study was to investigate the recovery of static and dynamic balance between the involved and the uninvolved sides.
Methods: The BBS (overall, anteroposterior index, and mediolateral index) and YBT (anterior, posterolateral, and posteromedial) of 58 patients underwent ACLR were measured one year postoperation. Both sides of the BBS and the YBT were compared using the paired t-test.
Results: All the index of the BBS showed no difference between the involved and the uninvolved sides, while all the scores of the YBT showed a significant difference in both sides. The YBT anterior result was 54.64 ± 5.62 cm in the involved side and 56.90 ± 5.41 cm in the uninvolved side (p = 0.001). The YBT posterolateral results were 90.12 ± 10.51 cm and 92.34 ± 9.85 cm (p = 0.013). The YBT posteromedial results were 93.72 ± 8.84 cm and 96.14 ± 9.37 cm (p = 0.002).
Conclusion: A year after ACLR, the static balance showed no difference, while the dynamic balance showed a significant difference in the involved and the uninvolved sides. The static balance of the involved side recovered as much as the uninvolved side, but the dynamic balance did not. Therefore, dynamic balance training should be considered in the rehabilitation program for patients underwent ACLR.

INTRODUCTION
MATERIALS AND METHODS
    1. Patients
    2. Surgical Techniques
    3. Postoperative Rehabilitation
    4. Y Balance Test
    5. The Biodex Balance System
    6. Statistical Analysis
RESULTS
DISCUSSION
CONCLUSIONS
ACKNOWLEDGEMENTS
CONFLICTS OF INTEREST
AUTHOR CONTRIBUTIONS
REFERENCES

• Jin-seong Kim(Sports Medical Center, Seoul Paik Hospital, Inje University College of Medicine)
• Moon-young Choi(Sports Medical Center, Seoul Paik Hospital, Inje University College of Medicine)
• Doo-hwan Kong(Sports Medical Center, Seoul Paik Hospital, Inje University College of Medicine)
• Kyu-sung Chung(Department of Orthopedic Surgery, Seoul Paik Hospital, Inje University College of Medicine, Seoul)
• Ui-jae Hwang(Department of Physical Therapy, College of Health Science, Yonsei University, Wonju, Korea)
• Oh-yun Kwon(Department of Physical Therapy, College of Health Science, Yonsei University, Wonju, Korea) Corresponding Author