The objective of this study was to examine the relationship of postural stability and lower extremity performance with core stability, knee laxity, and muscle strength in patients with anterior cruciate ligament reconstruction. Twenty-eight anterior cruciate ligament-reconstructed subjects participated in the study. Anterior knee laxity tests, isokinetic knee muscle strength tests, and core stability tests were performed. Single-limb postural stability was assessed in both eyes-open and eyes-closed positions on a static surface and an eyes-open condition on a foam surface. A single-legged hop test was performed to assess lower extremity performance. To detect differences between the operated and healthy leg, a Mann-Whitney U test was performed, and a correlation analysis was performed using the Spearman correlation coefficient. Knee muscle strength and laxity differed between the operated and healthy legs (P < 0.05). Postural stability scores correlated with core stability tests (P < 0.05) in the operated as well as healthy legs. In the operated leg, knee laxity and muscle strength correlated with the mediolateral sway index on a foam surface (P < 0.05). Knee flexor and extensor muscle strength correlated with the single-legged hop for both legs (P < 0.05).
Reductions in core stability, decreased knee muscle strength, and greater knee laxity correlated with single-limb postural stability. Better hop performance was demonstrated with better knee flexor and extensor muscle strength and was independent from core stability.