The goal of this [type of study: observational study] is to [detect concomitant KF and ALL injury in knees with ACL injury using MRI in both adult and pediatric patients and compare the effect of KF injury and multiple risk factors (concomitant injury to the ALL, medial collateral ligament [MCL], or anterior, central, or posterior part of the medial or lateral meniscus) on anterolateral rotatory laxity as measured by the pivot-shift test in a clinical setting.].

The main question [s] it aims to answer are:

[Does the main risk factor for a high-grade pivot shift after acute ACL injury differ between pediatric patients and adults?] [Does Concomitant KF injury significantly affect the pivot-shift phenomenon in pediatric patients with acute ACL injury?] Researchers will compare [71 pediatric patients and 469 adults] to see if [main risk factor for a high-grade pivot shift after acute ACL injury differs between pediatric patients and adults?].

Inclusion Criteria:

• unilateral acute primary ACL tear, considered when the patient reported knee injury occurring less than 2 weeks before the examination;
• bone bruising on the femoral condyles and tibial plateau identified on MRI.

Exclusion Criteria:

• concomitant ligament (posterior cruciate ligament and/or posterolateral complex) procedures or realignment procedures; contralateral knee injury;
• previous injury or surgery affecting the ipsilateral knee;
• insufficient data from the electronic medical record system;
• lack of KF visualization on MRI.

1994 patients were identified from medical records between Jan. 2019 and Dec. 2021. After reviewing the inclusion and exclusion criteria, 540 patients were included in the present study (71 pediatric patients and 469 adults).