Validity of Indirect Ultrasound Findings in Acute Anterior Cruciate Ligament Ruptures.

Abstract

Ultrasound (US) is increasingly being used as an extension of the physical examination on the sidelines, in training rooms, and in clinics. Anterior cruciate ligament (ACL) injury in sport is common, but the literature on US findings after acute ACL rupture is limited. Three indirect US findings of ACL rupture have been described, and this study assessed the validity of these indirect signs. Patients with an acute knee injury (<6 weeks) underwent US examinations to determine whether there was evidence of a femoral notch sign, posterior cruciate ligament wave sign, or capsular protrusion sign. Ultrasound findings were compared to magnetic resonance imaging. Sixty-nine patients were included (53 with ACL tears and 16 control patients). The posterior cruciate ligament sign had the highest sensitivity (84.9%), and the notch sign had the highest specificity (93.8%). If 2 or 3 of the signs were positive, the sensitivity was 86.8%, and the specificity was 87.5%. A US examination is an easy-to-perform and noninvasive test, and the 3 indirect signs of an acute ACL tear had high positive predictive values ranging from 91.8% to 96.8%.