Normal and acutely torn posterior cruciate ligament of the knee at US evaluation: Preliminary experience

PURPOSE: To determine the ultrasonographic (US) findings of normal and acut ely torn posterior cruciate ligament (PCL) of the knee and evaluate the use fulness of US in the injured PCL. MATERIALS AND METHODS: US images were obtained in 30 knees in 15 asymptomat ic volunteers as a control group and in 35 patients clinically suspected of having an acute PCL injury. Only the distal half of the PCL was evaluated. Of the 35 patients, 28 had their PCL status confirmed: 13 had a normal PCL at magnetic resonance (MR) imaging plus clinical examination, and 15 had a torn PCL at either MR imaging and surgery or MR imaging and clinical follo w-up. RESULTS: Normal PCLs were homogeneously hypoechoic, with a well-defined pos terior border. Torn PCLs were heterogeneously hypoechoic (12 [80%] of 15 pa tients), with an indistinct posterior margin (11 [73%] of 15 patients). Tor n PCLs were significantly thicker (range, 12.0-20.0 mm; mean, 15.6 mm +/- 2 .5 [SD]; P < .01), as compared with normal PCLs in 13 patients (range, 3.8- 5.8 mm; mean, 4.6 mm +/- 1.0; P < .01) and in the volunteers (range, 3.7-6. 2 mm; mean, 4.5 mm +/- 1.2; P < .01). CONCLUSION: An acutely torn PCL thickens (> 10 mm), loses its sharply defin ed posterior border, and has a heterogeneously hypoechoic appearance. US ma y be useful as a screening examination for patients suspected of having PCL injury and for deciding whether to perform more expensive MR imaging or su rgical intervention.