Idiopathic osteonecrosis versus osteochondritis dissecans of the knee: A retrospective ultrasound study

Abstract

In order to evaluate the role of ultrasonography to detect the osteochondral defects of the femoral condyles in idiopathic osteonecrosis and in osteochondritis dissecans, from January 1992 to June 1994 echography of the knee was performed on 21 patients. Fifteen patients had a diagnosis of osteonecrosis and six a diagnosis of osteochondritis dissecans (diagnosis made on the basis of X-ray and MRI findings). The sonographic study of the femoral condyles was made using a real time instrument equipped with a linear array probe of 7.5 MHz, with the patient in supine decubitus and the knee in maximum flexion. In order to make a graph of the alterations that can be evidenced echographicaly in two diseases, a ‘score’ based on the analysis of the subcondylar line is suggested. Ultrasound (US) has evidenced the anatomical alterations typical of each disease; this capacity together with clinical signs and the age of the patient allows the correct diagnosis. Sonography is faster than arthrography, arthroscopy, CT and MRI, is non-invasive and less expensive. Its drawback is that it does not detect small intraarticular bodies. We, therefore, believe that echography has a role in aseptic necrosis of the knee in the diagnosis and monitoring the course of the disease.