Sagittal Plane Knee Biomechanics and Vertical Ground Reaction Forces Are Modified Following ACL Injury Prevention Programs: A Systematic Review

CONTEXT: Injuries to the anterior cruciate ligament (ACL) occur because of excessive loading on the knee. ACL injury prevention programs can influence sagittal plane ACL loading factors and vertical ground reaction force (VGRF). OBJECTIVE: To determine the influence of ACL injury prevention programs on sagittal plane knee biomechanics (anterior tibial shear force, knee flexion angle/moments) and VGRF. DATA SOURCES: The PubMed database was searched for studies published between January 1988 and June 2008. Reference lists of selected articles were also reviewed. STUDY SELECTION: Studies were included that evaluated healthy participants for knee flexion angle, sagittal plane knee kinetics, or VGRF after performing a multisession training program. Two individuals reviewed all articles and determined which articles met the selection criteria. Approximately 4% of the articles fulfilled the selection criteria. DATA EXTRACTION: Data were extracted regarding each program’s duration, frequency, exercise type, population, supervision, and testing procedures. Means and variability measures were recorded to calculate effect sizes. One reviewer extracted all data and assessed study quality using PEDro (Physiotherapy Evidence Database). A second reviewer (blinded) verified all information. RESULTS: There is moderate evidence to indicate that knee flexion angle, external knee flexion moment, and VGRF can be successfully modified by an ACL injury prevention program. Programs utilizing multiple exercises (ie, integrated training) appear to produce the most improvement, in comparison to that of single-exercise programs. Knee flexion angle was improved following integrated training (combined balance and strength exercises or combined plyometric and strength exercises). Similarly, external knee flexion moment was improved following integrated training consisting of balance, plyometric, and strength exercises. VGRF was improved when incorporating supervision with instruction and feedback on proper technique. CONCLUSION: ACL injury prevention programs that are aimed at modifying sagittal plane knee biomechanics and VGRF should use an integrated training approach that incorporates instruction and feedback on proper movement technique.