The Anteromedial Tibial Rim Sign

An Indicator of Patellotibial Impaction in Acute Anterior Cruciate Ligament Tears

Abstract

Objective 

We have encountered unexplained anteromedial tibial rim edema in acute anterior cruciate ligament (ACL) tears. Our goal was to determine the incidence, internal derangements, and mechanism of injury in patients with anteromedial tibial rim edema (rim sign).

Materials and Methods 

A retrospective review of ACL tears diagnosed by magnetic resonance imaging over 7 years was performed. Patients were dichotomized into those with and without a rim sign.

Results 

There were 132 acute ACL tears. Individuals with a rim sign (31, 23%) had more contusions, fractures, ligament tears (P < 0.001), posterolateral corner injuries (P = 0.001), and posterior horn lateral meniscus tears (P = 0.042) than those without. Five individuals demonstrated edema in the inferior patella, consistent with patellotibial impaction.

Conclusions 

The rim sign is common in ACL tears, indicating greater internal derangement. The rim sign represents patellotibial impaction with edema rarely present in the patella.