Chondral and osteochondral injuries are relatively common in the weightbearing joints of the lower extremity. The pathology can range from a simple contusion of the articular cartilage and subchondral bone to a fracture involving the cartilage alone or cartilage and underlying subchondral bone together. The mechanism of injury is from one of three types of trauma: compaction, shearing, or avulsion.<sup>26Mow V.C., Zhu W., Ratcliffe A. Structure and function of articular cartilage and meniscus Basic Orthopaedic Biomechanics New York: Raven Press (1991).  143-198

Cliquez ici pour aller à la section Références</sup> Because the injury is usually subtle and causes little to no dysfunction, the diagnosis of acute injuries is delayed. Occasionally, the injury is severe enough to cause a significant effusion, hemarthrosis, or ligament disruption. Even in such cases, the osteochondral injury often goes undiagnosed. In the past, plain radiography, arthrography, and joint aspiration were the only diagnostic modalities available to the clinician. Plain radiographs are not sensitive because the bone fragment tends to be small even when a large osteochondral defect is present. An arthrogram is quite good at detecting the defect; however, because it is an invasive study, a high index of suspicion is needed to justify its use. Joint aspiration is also invasive, but can demonstrate the presence of a hemarthrosis with fat droplets, indicative of an intraarticular fracture; however, aspiration cannot define the size or location of the injury. Recently, magnetic resonance (MR) imaging has been used to demonstrate marrow changes consistent with trabecular microfracture; MR imaging can be used to evaluate the size and location of the injury. This should make earlier diagnosis and treatment of these lesions easier, leading to a better functional outcome for the patient.