54 ACL injury patients originally randomized to receive rehabilitation involving physiotherapy with or without reconstruction surgery were included in this follow-up study for the purpose of determining significant associations between patient-reported outcomes (including function, knee-related quality of life, and postural balance) and lower extremity muscle function, when assessed after a mean of 3 years post-therapy. Results demonstrated that lower extremity muscle function at 3 years was significantly associated with patient-reported knee outcomes at 5 years regardless of original rehabilitation allocation.