The posterior oblique ligament in MRI of acute knee trauma

To identify the posterior oblique ligament and assess incidence and patterns of injury to the ligament on MRI of acute knee trauma.

One hundred twenty-three MRI studies met the study criteria. For each case, the posterior oblique ligament was identified and scored as injured or normal. Incidence of proximal and distal posterior oblique ligament tears was calculated. Fisher's tests were employed to determine significance of association between tears of the posterior oblique ligament and components of the posteromedial corner and other capsuloligamentous structures of the knee.

The posterior oblique ligament was reliably identified as a distinct structure in 123 MRI scans that met the criteria and was consistently labeled as intact or torn. Posterior oblique ligament tear was seen in 61.7% of knee trauma with proximal injury in 56.5% and distal injury in 97.3% of positive cases. Posterior oblique ligament disruption was a part of multiligamentous injury in 94.7% of positive cases. Posterior oblique ligament injuries (n = 76) had an extremely significant relationship with oblique popliteal ligament tears (n = 27) (p = 0.0001), semimembranosus tendon insertion tears (n = 15) (p = 0.0005), and medial collateral ligament tears (n = 15) (p = 0.0005) and a highly significant association with medial meniscus tears (n = 68) (p = 0.0049) and posterior cruciate ligament tears (n = 12) (p = 0.0033). The association with anterior cruciate ligament tears (n = 53) was not significant.

The posterior oblique ligament is a distinct radiological entity consistently identified in acute trauma MRI. Disruptions of the distal posterior oblique ligament are frequent in complex knee injury, notably in association with oblique popliteal ligament, medial collateral ligament, and semimembranosus tendon tears.