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Am J Sports Med. 2011 Nov;39(11):2347-54. doi: 10.1177/0363546511417085. Epub 2011 Aug 9.

Single-legged hop tests as predictors of self-reported knee function in nonoperatively treated individuals with anterior cruciate ligament injury.

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  • 1Norwegian Research Center for Active Rehabilitation, Hjelp24 Norwegian Sports Medicine Clinic, Ullevål Stadion, Norway.



Previous studies have found significant predictors for functional outcome after anterior cruciate ligament (ACL) reconstruction; however, studies examining predictors for functional outcome in nonoperatively treated individuals are lacking.


Single-legged hop tests predict self-reported knee function (International Knee Documentation Committee [IKDC] 2000) in nonoperatively treated ACL-injured individuals 1 year after baseline testing.


Cohort study (prognosis); Level of evidence, 2.


Ninety-one nonoperatively treated patients with an ACL injury were tested using 4 single-legged hop tests on average 74 ± 30 days after injury in a prospective cohort study. Eighty-one patients (89%) completed the IKDC 2000 1 year later. Patients with an IKDC 2000 score equal to or higher than the age- and gender-specific 15th percentile score from previously published data on an uninjured population were classified as having self-reported function within normal ranges. Logistic regression analyses were performed to identify predictors of self-reported knee function. The area under the curve (AUC) from receiver operating characteristic curves was used as a measure of discriminative accuracy. Optimal limb symmetry index (LSI) cutoff for the best single-legged hop test was defined as the LSI with the highest product of sensitivity and specificity.


Single hop for distance symmetry indexes predicted self-reported knee function at the 1-year follow-up (P = .036). Combinations of any 2 hop tests (AUC = 0.64-0.71) did not give a higher discriminative accuracy than the single hop alone (AUC = 0.71). A cutoff of 88% (LSI) for the single hop revealed a sensitivity of 71.4% and a specificity of 71.7%.


The single hop for distance (LSI) significantly predicted self-reported knee function after 1 year in nonoperatively treated ACL-injured patients. Combinations of 2 single-legged hop tests did not lead to higher discriminative accuracy than the single hop alone.

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