Ultrasound assessment of internal derangement of the knee.

In a prospective double-blind study we investigated internal knee disorders with ultrasound and compared the results with Magnetic Resonance Imaging (MRI) and arthroscopy. The aim was to determine the effectiveness of ultrasound in diagnosing Internal Derangement of the Knee (IDK) and to compare the results with MRI. Over an 18-months period, 81 patients were examined. All were male; they had a mean age of 35 years. For various technical reasons 21 patients were subsequently excluded from the study. After initial clinical examinations, patients had an ultrasound and MRI scan at the same visit. Arthroscopy was performed within a month of this. Different radiologists who were unaware of the clinical findings independently reported on the ultrasound and MRI. The surgeon performing the arthroscopy was made aware only of the MRI findings. Structures accessed were the lateral and medial menisci and the anterior (ACL) and posterior (PCL) cruciate ligaments. Arthroscopy was taken as the gold standard. Ultrasound showed good sensitivity, ranging from 76% for the ACL to 90% for the medial meniscus, and excellent specificity, ranging from 92% for the medial meniscus to 100% for the ACL. Accuracy ranged from 86% for the ACL to 98% for the lateral meniscus. These figures were comparable to the MRI findings. We concluded that ultrasound is a simple, accurate, inexpensive and non-invasive way of assessing internal knee disorders. There is a learning curve, but results are similar to MRI.