Correlation between dynamic postural stability and muscle strength, anterior instability, and knee scale in anterior cruciate ligament deficient knees

Aim The purpose of this study was to assess the correlations between dynamic postural stability and muscle strength, anterior instability, and knee scores in anterior cruciate ligament (ACL) deficient knees. Method We examined 40 male patients with ACL injury prior to surgery. Maximal torques of flexors and extensors of the injured knee at 60 and 180 degrees/s were evaluated using an isokinetic testing device. Anterior translations of the tibia were measured using a KT-2000 arthrometer, and dynamic postural stabilities were measured during single-leg stance using the Biodex Stability System (BSS). Knee statuses were evaluated using Lysholm and International Knee Documentation Committee (IKDC) knee scores. Correlations between dynamic postural stability and muscle strength, anterior instability, and knee scores were determined. Results Significant correlations were found between maximal torques of the extensor of injured knees at 60 and 180 degrees/s (r = -0.52, p = 0.048 and r = -0.46, p = 0.019, respectively) and dynamic postural stability, and maximal torques of flexors of injured knees showed similar relations (r = -0.51, p = 0.0048 and r = -0.47, p = 0.016, respectively). Lysholm and IKDC knee scores were also found to be correlated with dynamic postural stability (r = -0.49, p = 0.001 and r = -0.52, p = 0.005, respectively). However, no correlation was found between grade of anterior translation measured using the KT-2000 arthrometer and dynamic postural stability (p = 1.0). Conclusion Dynamic postural stability determined using the BSS appears to be influenced by muscle strength, as determined by isokinetic testing, but not with grade of anterior translation measured using a KT-2000 arthrometer. Subjective knee scores appear to improve in parallel with dynamic postural stability.