EASILY MISSED INJURIES AROUND THE KNEE

Most fractures around the knee are easily detected on high-quality rad iographs. However, some fractures and musculotendinous and ligamentous injuries have subtle findings and may be difficult to detect even wit h optimal images; these injuries include tibial plateau fractures, Seg ond fractures, stress fractures, fibular head fractures and dislocatio ns, injuries to the patella and extensor mechanism, and Salter type fr actures. Clinically suspected tibial plateau fractures unseen on stand ard views may be seen on tangential or tunnel projections. Segond frac tures usually have a characteristic appearance on anteroposterior radi ographs but occasionally are seen only on tunnel views. Stress fractur es of the proximal tibia may be accompanied by a vague band of increas ed sclerosis or endosteal callus on either side of the epiphyseal scar . Correct diagnosis of fibular head dislocations requires clinical sus picion, since these injuries often are not recognized on initial radio graphs. Careful evaluation of the congruity of the tibiofibular joint on the lateral projection is the key to diagnosis. Vertical patellar f ractures are often nondisplaced and are best evaluated with sunrise or Merchant views; avulsion fractures from the proximal or distal poles, with lateral views; and osteochondral fractures, with sunrise or inte rnal oblique views. Salter I injuries can be visualized on oblique and anteroposterior views obtained with stress applied to the knee. Some occult Salter I fractures are diagnosed on follow-up radiographs, whic h show periosteal reaction. Imaging modalities other than radiography are rarely needed to diagnose fractures but are useful for evaluating the extent of displacement or confirming soft-tissue injuries.