[Intra-osseus hidden fractures of the knee in athletes: assessment with magnetic resonance imaging].

The diagnostic capabilities of Magnetic Resonance Imaging (MRI) were investigated in the study of occult intraosseous fractures of the knees in athletes; this pathologic condition is difficult to assess with conventional diagnostic techniques. Twelve athletes were considered and submitted to MR examinations 1-8 days after trauma. All patients had undergone plain films, 6 of them CT and 3 scintigraphy. Four patients were followed with MRI at 15 and 30 days. Plain films were negative in all patients. On CT, in one case only an area of segmental osteoporosis was identified at the anterolateral tibial plateau. Scintigraphy provided positive but aspecific results in all three patients. MRI demonstrated all lesions: 3 at the tibial plateau, 5 at the lateral femoral condyle and 2 at the medial femoral condyle. Double localizations were observed in two patients, femorotibial and tibiopatellar, respectively. In no case lesions of meniscal and/or capsuloligamentous structures of the knee were associated. Arthroscopy, which was employed in two patients, confirmed MR diagnosis. Thanks to its high spatial and contrast resolution and to its multiplanar capabilities, MRI can be considered the method of choice in the study of occult intraosseous fractures of athletes' knees. Beside localizing the lesion site, MRI allows the evaluation of its extent (linear or reticulo-geographic patterns) and the exclusion of possible involvement of meniscal and/or capsulo-ligamentous structures. MRI follow-up of this condition showed the "restitutio ad integrum" of the medullary trabecular bone as early as at 15 and 30 days, depending on lesion pattern and extent. On the basis of our experience, MRI emerges as the only diagnostic technique allowing the accurate evaluation of occult intraosseous fractures of the knee in athletes, because it provides early and detailed information which is valuable for the therapeutic approach, which is of fundamental importance to resume sports activity quickly.