Objectives: To define the accuracy (compared with magnetic resonance imaging [MRI]) of sonographic examination in detecting knee effusion and to determine whether the presence of knee effusions in patients with traumatic knee injury can predict knee internal derangement as assessed by MRI.
Design: Prospective study.
Setting: Hospital rehabilitation department.
Participants: Thirty patients (19 men, 11 women) with traumatic knee injury were recruited. Subjects received sonographic examination and MRI on the same day.
Interventions: Not applicable.
Main outcome measures: The presence or absence of knee effusion was assessed by sonographic examination. MRI was used as criterion standard to evaluate whether the presence of knee effusion and internal derangement, which included tear of anterior and posterior cruciate ligaments, as well as meniscus tear.
Results: The sensitivity of sonographic examination for detecting knee effusion was 79.1%, and specificity was 50%. The positive-predictive value (PPV) was 86.3% and negative-predictive value (NPV) was 37.5%. The PPV of sonographic effusion to internal derangement was 90.9%, and the NPV was 37.5%.
Conclusions: Sonographic examination can accurately detect effusion of the knee. The detection of knee effusion in patients with traumatic knee injury by sonographic examination is highly indicative of internal knee derangement.