Lateral-compartment bone contusions in adolescents with intact anterior cruciate ligaments.

Purpose: To determine how often lateral-compartment bone contusions are seen on magnetic resonance (MR) images of knees in adolescents with intact anterior cruciate ligaments (ACLs).
Materials and Methods: MR images obtained in 53 adolescent patients (30 male, 23 female; aged 10-20 years) were reviewed to detect bone contusions in the posterolateral tibial plateau or the lateral femoral condyle. ACLs were also evaluated with accepted criteria for the diagnosis of ligamental disruption. Only patients referred for evaluation of a knee injury or mechanical symptoms were included.
Results: Five patients with bone contusions had an intact ACL at MR imaging. One of the five had arthroscopic confirmation. Fifteen other patients had complete ACL disruptions: 13 of these patients had typical bone contusions; the other two had no bone abnormalities but had chronic ACL tears. Thus, 28% of the 18 patients with typical bone contusions had intact ACLs.
Conclusion: Adolescents may have the same pattern of contusions as adults but may maintain an intact ACL owing to increased ligamentous laxity.