Overcoming barriers faced by practitioners in assessing ACL injury risk

 An anterior cruciate ligament (ACL) rupture is one of the most severe injuries within multidirectional field sports, resulting in long durations away from training and matches. This can have negative short and long-term outcomes that impact all stakeholders (players, coaches, owners, teams). Most ACL ruptures are non-contact in nature, predominantly occurring during the braking phase of a landing from a jump or a change of direction manoeuvre (e.g., a cut). As such, assessing an athlete’s movement strategies during tasks which replicate common ACL injury mechanisms (such as a bilateral and unilateral drop jump, and a cut) may provide practitioners the opportunity to identify athletes who are displaying biomechanics associated with ACL injury. However, there are barriers that practitioners face that limits their ability to regularly assess an athlete’s movement strategy, and thereby, ACL injury risk. These barriers must be overcome for practitioners to accurately assess an athlete’s movement strategy in the field and target potential biomechanics associated with ACL injury. Due to the large overall number of male athletes participating in multidirectional field sports, males account for the highest absolute number of ACL injuries. Therefore, the purpose of this thesis was to improve the ability of practitioners to regularly assess ACL injury risk in applied field-based settings, by targeting common barriers faced by practitioners.

The first study found a movement strategy correspondence between the bilateral and unilateral drop jump, but not between the unilateral drop jump and the cut. To increase the efficiency of practitioner ACL injury risk assessments, practitioners could consider omitting one of the drop jumps from ACL injury risk assessments to avoid task redundancies, although the cut should be included as this provides additional information using a sport-specific movement. Additionally, the second study observed differences in knee RoM, moments and stiffness between ACLR patients and non-injured controls which may contribute to ACL injury. Practitioners should therefore include measurements of these variables in ACL injury risk assessments to identify athletes who may be at higher risk of ACL injury. However, biomechanical variables can be difficult for practitioners to measure in the field, and thus, there was a need to examine more easily accessible field-based technologies to enable practitioners to assess an athlete in applied field-based settings. Subsequently, study three revealed that angular velocities and accelerations obtained from a tibia located IMU can be used as proxy measures of knee moments, RoM and stiffness in movements used by practitioners to assess ACL injury risk. Furthermore, the surface on which practitioner assessments of ACL injury iv risk are performed on is typically not the surface athletes train and play matches on. The final study found that biomechanical variables associated with ACL injury risk were predominantly more pronounced in practitioner assessments of ACL injury risk performed on a harder surface, compared to the same movements performed on a softer more cushioned surface that is typically used for training and/or matches (e.g., artificial turf). Practitioners should be aware that surface hardness influences an athlete’s movement strategies and may misrepresent their risk of ACL injury. Therefore, practitioners should consistently test on one surface to accurately identify true changes in an athlete’s movement strategies between regular ACL injury risk assessments.

Together these findings have further developed the ability of practitioners to regularly assess ACL injury risk in applied field-based settings by overcoming barriers they face. Subsequently, practitioners can identify athletes who may be at higher risk of first or second ACL injury and facilitate appropriate interventions or rehabilitation programmes, respectively. Ultimately, this may help to reduce the overall number of non-contact ACL injuries within male multidirectional field sport athletes.