Is MRI effective in detecting intraarticular abnormalities of the injured knee?

Magnetic resonance imaging (MRI) is widely used for the diagnosis of intraarticular anomalies of the knee. Its reliability is controversial mainly in the pediatric population, and its results may vary from one center to the other. The purpose of this study was to assess the validity of MRI in detecting intraarticular abnormalities in patients who sustained an injury of their knee, by comparing its findings to those of arthroscopy.

Two hundred and seventeen traumatic knees underwent MRI followed by arthroscopy. Findings of MRI and arthroscopy were statistically compared.

Accuracy of MRI was 95.39% and 99.08% for anterior and posterior cruciate ligament ruptures respectively, 85.25% and 90.78% for medial and lateral meniscal tears respectively, and 91.24% for injury of the articular cartilage. There was not a significant difference between the pediatric and the adult populations, except for a greater sensitivity to detect lateral meniscal tears and a better specificity and accuracy to identify chondral lesions in the first group. Variability between centers was significant for the diagnosis of chondral defects.

The good MRI reliability in detecting intraarticular abnormalities as demonstrated in this report, underlines its importance in the assessment of the injured knee before arthroscopy.