Ultrasonographic diagnosis of the posterior cruciate ligament injury in a 4-year-old child: a case report.

Posterior cruciate ligament (PCL) injury is a rare condition in children. We report a 4-year-old child with an isolated rupture of PCL in which diagnosis is made by ultrasonography (US). Magnetic resonance imaging is highly sensitive and specific in the diagnosis of PCL injuries and provides useful information about other potentially injured structures, but PCL can also be evaluated sonographically. Findings that should be looked for include enlargement or focal disruption of the ligament by comparison with the contralateral normal PCL. US may be a useful examination tool in children with a suspected PCL injury.