Introduction: We evaluated the effect of electromyography biofeedback on proprioception and functional balance in healthy young athletes. Materials and Methods: In this clinical trial, 24 athletes were randomly divided into two study (n=12) and control (n=12) groups. The study group received rehabilitation exercises, including one-foot standing, squatted standing, and isometric contraction of quadriceps muscle at different knee angles, including 30, 45, and 90 degrees of knee flexion along with electromyography biofeedback. The control group received only rehabilitation exercises without electromyography biofeedback. Exercises were performed by both groups for a 4-week period in three sessions per week. Functional balance and proprioception before and after exercises were measured using the star excursion balance test and a system consisting of digital photography non-reflective markers, respectively. The data of the center of pressure and time of vertical ground reaction force using a force plate was also collected to evaluate static balance and dynamic balance, respectively. Results: The absolute error in knee joint reconstruction for 30° (P=0.005),  45°  (P=0.001),  and 90° (P=0.033) angles significantly decreased after the intervention in the study group compared to the control group. Star excursion balance test scores in all directions did not show any significant differences between the two groups (P>0.05), except for the anterior-lateral direction (P=0.03). Moreover, all variables related to static and dynamic balance did not show a significant difference between two the groups after the interventions (P>0.05). Conclusion: The electromyography biofeedback intervention can probably be used as a rehabilitation protocol in recovering and healing proprioception injuries resulting from sports injuries.

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Introduction: In addition to the instability of the knee joint, injury to the anterior cruciate ligament (ACL) leads to a functional deficit in the form of diminished proprioception of the knee joint. The purpose of this study was to compare knee proprioception in athletes with an ACL injury and healthy athletes. Materials and Methods: The participants  in this cross-sectional  study were 26 athletes  with an ACL injury and 24 healthy athletes who were selected from the orthopedic clinic at Baqiyatallah Hospital in 2019, Tehran City, Iran. Cooper or non-Cooper subjects with ACL injury were identified via the knee injury and osteoarthritis outcome score (KOOS). The  knee proprioception of all participants was recorded using a system consisting of digital photography, non-reflective markers, and Digimizer software. Results: The results showed that there was no significant difference between groups in the absolute error of knee joint reconstruction at both 45° and 90° angles. Conclusion: The data of the study showed that in comparison with healthy athletes, the knee joint proprioception of athletes with an ACL injury is not different and has the same function.