Introduction The outcome following operative or non-operative treatment of ACL injuries in children is traditionally assessed by patient reported outcome measures (PROMs), functional performance tests and clinical measurements (e.g. instrumented laxity). However, there is little evidence as to whether these different types of outcome are complementary to evaluate the condition, or if each outcome is representative for how the child is doing.

Materials and Methods A consecutive group of children (defined as < 16 years old) who had an ACL-reconstruction, were prospectively followed and assessed after 1-year with Pedi-IKDC and KOOS-Child, instrumented laxity measurement, range of motion, extension strength and four performance tests. By partial correlation coefficient analysis, controlling for age, height and weight, correlations between the different outcomes were calculated.

Results In the group of 163 children, 141 had all assessments necessary for the analysis. There were weak to strong correlations between the scores from Pedi-IKDC and the scores from each of the 5 domains of KOOS-Child and a weak to moderate correlation between the different domains of KOOS-Child. Similar correlations were found between the different performance tests. There were only few positive and weak correlations between performance tests and PROMS and between clinical measurements and PROMS.

Conclusion For children who had their ACL reconstructed there was no clinically important correlation between scores obtained by PROMs, a battery of functional performance tests and instrumented laxity of the knee at 1-year follow-up postoperatively. This is an argument for always to include and report all three types of outcomes.