Elana Amir

Lesions to the anterior cruciate ligament, or ACL, have increased significantly in recent years.

These traumatic events have ubiquitous prevalence in sports, and athletes are at the highest risk for tearing their ACL; specifically those who play soccer, football, basketball, or volleyball. Women and the very young are also at risk for rupture and re-rupture of the ACL. ACL injury results from a sudden movement of lateral flexion and external/internal rotation (5). A sudden change in direction or a sharp deceleration would lead to pain, instability, and swelling. These are the typical signs of acute ACL injury.

ACL injury leads to loss of joint stability, and an injury in this ligament can cause damage to other joint structures in the leg. ACL surgery is major, as it involves reconstructing or replacing this ligament of the knee. However, nonoperative management of ACL tears is not well tolerated and often leads to recurrent instability and more injuries (2). Multiple types of ACL reconstruction and repair methods exist in practice and all of them have a recovery phase from six months to upwards of two years. Rehabilitation is recommended and necessary as the primary course of treatment after ACL injury. Proper rehabilitation therapy strongly correlates to a more optimal and higher quality recovery from ACL reconstruction.

Studies have found that the rehabilitation process can be made even more effective through the use of biofeedback technology. Mobility and strength training specifically can be improved during rehabilitation using a biofeedback mechanism. Following ACL injury, loss of knee extension is frequently found. One study specifically examined the addition of Electromyographic Biofeedback (EMG BFB) therapy in the early phase of the rehabilitation for 16 patients who recently underwent reconstruction surgery. Biofeedback was found to improve the range of knee extension and strength after ACL reconstruction, specifically the measures of passive knee extension and high heel distance (1).

Another study described that while conventional prevention programs focus on reducing knee abduction load and posture during dynamic activity, targeting hip extensor strength and utilization may be more effective. This especially relates to the underlying mechanism of the injury in adolescent female athletes. The researchers hypothesized that biofeedback training may complement traditional preventive training and may be needed to maximize the effectiveness of interventions (4). There is limited efficacy with current existing injury prevention programs and hence this novel, objective, and real-time interactive visual feedback system is well designed to reduce risk factors.

Biofeedback was in fact found to decrease the risk factors for sustaining second ACL injury. Another study similarly looked at ways to modify rehabilitation to improve movement and loading symmetry. Visual and tactile biofeedback interventions were developed and used on 40 adolescent ACLR patients enrolled in the trial. The primary method was a 6-week biofeedback training program focused on improving loading and movement symmetry during bilateral squatting in biweekly intervention sessions. The program provided sensory (visual and tactile) feedback to the participant to heighten awareness of asymmetrical movement strategies (e.g. load shift, decreased movement symmetry) and neuromuscular control during a squat.

The two exercises that were completed during the biofeedback training program were a visual feedback squat and a resisted squat (tactile feedback). These methods demonstrated the ability to alter loading symmetry with visual feedback during a squatting task, for example. This approach implemented during the preliminary clinical trial was expected to result in improved knee extension moment symmetry at post-intervention with the biofeedback group compared to the control group (3).

Nearly 1 in 60 adolescent athletes will suffer ACL injuries with 90% of these athletes choosing to undergo a reconstruction (3). Rehabilitation after reconstruction has the goal of restoring joint stability, but many patients will suffer a second ACL tear. Current therapeutic interventions have not been effective in decreasing this incidence. Using new techniques such as biofeedback could increase neuromuscular control while decreasing risk factors for second ACL injuries. The studies exploring this idea will provide the foundation for future studies required to change post-operative rehabilitation methods to include innovative biofeedback training programs.

This article has been reviewed and approved by the Scientific Writing Team Lead of Esurgi : Ishtiak Ahmed Chowdhury


  1. Christanell F, Hoser C, Huber R, Fink C, Luomajoki H. The influence of electromyographic biofeedback therapy on knee extension following anterior cruciate ligament reconstruction: a randomized controlled trial. Sports Med Arthrosc Rehabil Ther Technol. 2012;4(1):41. Published 2012 Nov 6. doi:10.1186/1758-2555-4-41
  • Raines BT, Naclerio E, Sherman SL. Management of Anterior Cruciate Ligament Injury: What’s In and What’s Out?. Indian J Orthop. 2017;51(5):563-575. doi:10.4103/ortho.IJOrtho_245_17
  • Queen RM, Peebles AT, Miller TK, et al. Reduction of risk factors for ACL re-injuries using an innovative biofeedback approach: Rationale and design. Contemporary Clinical Trials Communications. 2021;22:100769. doi:10.1016/j.conctc.2021.100769
  • Taylor, J.B., Nguyen, AD., Paterno, M.V. et al. Real-time optimized biofeedback utilizing sport techniques (ROBUST): a study protocol for a randomized controlled trial. BMC Musculoskelet Disord 18, 71 (2017). https://doi.org/10.1186/s12891-017-1436-1
  • The usage of the biofeedback to take care of ACL. CoRehab.

https://www.corehab.it/en/biofeedback_chinelab_case_acl/. Published September 13, 2019. Accessed September 30, 2021.