Anterior and posterior cruciate ligaments at different patient ages: MR imaging findings

Purpose: To retrospectively compile normative data on the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL) in children and young adults.

Materials and methods: This HIPAA-compliant study was approved by the institutional review board. The requirement for informed patient consent was waived. Knee MR imaging examinations (n = 324) were performed in 168 female and 156 male patients (age range, 1-20 years) at 1.5 and 3.0 T, and the image findings were retrospectively evaluated by two blinded radiologists separately. One radiologist reviewed all images twice at two sessions, and the other reviewed a random subset of half the images during one session. Discordant assessments were resolved by consensus. The sagittal and coronal ACL-tibial angles, Blumensaat line-ACL angle, angle of inclination of the intercondylar roof, ACL-tibial insertion site, and PCL angle and horizontal component-to-vertical component ratio were measured. The associations between these values and patient age, patient sex, and physeal patency were assessed. Linear and fractional polynomial regression models were used to evaluate the relationships between measurements.

Results: ACL-tibial angles became significantly larger (P < .001) with increasing age during skeletal growth and approached adult values after physeal fusion. The Blumensaat line-ACL angle was constant after age 2 years. The inclination of intercondylar roof angle became significantly smaller (P < .001) with increasing age. The ACL-tibial insertion site was constant at the junction of the anterior and middle thirds of the tibial anteroposterior diameter and was not age dependent. The PCL angle became significantly larger (P < .001) with advancing age and in children who had fused as opposed to open physes. The horizontal component-to-vertical component PCL ratio became significantly smaller with advancing age (P < .001).

Conclusion: During growth, angulation of the ACL is age dependent. The angle and morphologic changes of the PCL are age dependent throughout skeletal maturation.