The role of the posterior oblique ligament in controlling posterior tibial translation in the posterior cruciate ligament-deficient knee.

BACKGROUND

Posterior cruciate ligament injuries are often associated with injuries to other structures. The role of the posteromedial structures of the knee in these injuries has received little attention.

HYPOTHESIS

The posterior oblique ligament is an important restraint to posterior tibial translation in the posterior cruciate ligament-deficient knee.

STUDY DESIGN

Controlled laboratory study.

METHODS

Kinematic studies were performed on 10 cadaveric knees to test 3 external loading conditions at 0 degrees , 30 degrees , 60 degrees , and 90 degrees of flexion (134 N posterior tibial load, 10 N x m valgus rotation, and 5 N x m internal rotation). Resulting posterior tibial translation was determined by using a robotic/universal force-moment sensor testing system for (1) intact, (2) posterior cruciate ligament-deficient, (3) posterior cruciate ligament/superficial medial collateral ligament-deficient, (4) posterior cruciate ligament/superficial medial collateral ligament/deep medial collateral ligament/posterior oblique ligament-deficient, and (5) posterior cruciate ligament/superficial medial collateral ligament/deep medial collateral ligament/posterior oblique ligament/posteromedial capsule-deficient knee.

RESULTS

When both the superficial medial collateral ligament and deep medial collateral ligament were cut in the posterior cruciate ligament-deficient knee, posterior tibial translation did not increase significantly at any flexion grade under all external loading conditions (P > .05). Additional cutting of the posterior oblique ligament increased posterior tibial translation significantly at 0 degrees , 30 degrees , 60 degrees , and 90 degrees of flexion under posterior tibial load and at all flexion angles tested under valgus or internal tibial load (P < .05). Additional cutting of the posteromedial capsule increased posterior tibial translation only at 0 degrees and 30 degrees in response to a valgus and internal tibial load (P < .05).

CONCLUSION

The posterior oblique ligament and posteromedial capsule have a significant role in the prevention of additional posterior tibial translation in the knee with posterior cruciate ligament injury.

CLINICAL RELEVANCE

The posterior oblique ligament should be addressed in the patient with combined injuries to the posterior cruciate ligament and the posteromedial structures.