ACL Injury – June 2018

by Michael Wang, MD

13 year-old soccer player with impact to lateral knee.

What are the findings?

Findings

A

A) Discontinuous ACL with lax/wavy fibers and surrounding edema.

B

B) Bone contusions at the lateral femoral condyle and tibial plateau.

C

C) A different patient, also a soccer player, with a torn ACL.

D

D) A loose body posteriorly (likely an avulsion fragment) in the same patient as in C)

Discussion

This patient suffered a blow to the lateral knee which resulted in a complete tear of the ACL.

She also had small bone contusions of the lateral femoral condyle and posterior tibial plateau which are characteristic of this internal derangement.

The remaining ligaments, menisci and cartilage were intact. In the “terrible triad” – ACL tear, MCL tear and medial meniscus tear are often seen together.

In our other example a loose body is seen posteriorly to the distal femur which is probably an avulsion fragment from the proximal ACL. Avulsion injuries are more common in the pediatric population compared to adults, because ligaments and tendons are relatively stronger than their attachments in the pediatric population whereas in adults chronic injury of ligaments and tendons predispose them to tears.