Significance of the single-legged hop test to the anterior cruciate ligament-reconstructed knee in relation to muscle strength and anterior laxity.

We investigated the significance of the single-legged hop test to the anterior cruciate ligament-reconstructed knee as it specifically relates to knee muscle strength recovery and residual anterior laxity. The hop test was conducted on 107 patients with unilateral anterior cruciate ligament-reconstructed knees (78 semitendinosus tendon autografts and 29 bone-patellar tendon-bone autografts). Patients were tested an average of 2 years after surgery. Correlation coefficient analyses determined whether the relationship between knee muscle strength recovery and the hop test was invariant across all levels of residual anterior laxity and whether the relationship between residual anterior laxity and the hop test was invariant across levels of quadriceps muscle strength recovery. Furthermore, we examined the effect of graft harvest site on the hop index. Positive correlations were found between the hop index and muscle strength index at all levels of residual anterior laxity (P < 0.05), but these correlation coefficients were relatively low. There were no apparent correlations between the hop index and residual anterior laxity at all levels of quadriceps muscle strength recovery. There was no significant difference in the average hop index between the semitendinosus tendon autograft group and the bone-patellar tendon-bone autograft group.