Background: One of the most useful clinical
tests for diagnosing an isolated injury of the posterior cruciate
ligament is the posterior drawer maneuver performed with the knee
in 90° of flexion. Previously, it was thought that internally rotating
the tibia during posterior drawer testing would decrease posterior
laxity in a knee with an isolated posterior cruciate ligament injury.
In this study, we evaluated the effects of internal and external tibial
rotation on posterior laxity with the knee held in varying degrees
of flexion after the posterior cruciate and meniscofemoral ligaments
had been cut.
Materials and Methods: Twenty cadaveric knees were
used. Each knee was mounted in a fixture with six degrees of freedom,
and anterior and posterior forces of 150 N were applied. The testing
was conducted with the knee in 90°, 60°, 30°, and 0° of flexion
with the tibia in neutral, internal, and external rotation. All
knees were tested with the posterior cruciate and meniscofemoral ligaments
intact and transected. Repeated-measures analysis of variance was
used for statistical analysis.
Results: At 30°, 60°, and 90° of flexion, there
was a significant increase in posterior laxity following transection
of the posterior cruciate and meniscofemoral ligaments. At 60° and
90° of flexion, there was significantly less posterior laxity when
the tibia was held in internal compared with external rotation.
At 0° and 30° of flexion, there was no significant difference in posterior
laxity when the tibia was held in internal compared with external
Conclusions: After the posterior cruciate and meniscofemoral
ligaments had been cut, posterior laxity was significantly decreased
by both internal and external rotation of the tibia. Internal tibial rotation
resulted in significantly less laxity than external tibial rotation
did at 60° and 90° of knee flexion.
Clinical Relevance: An isolated injury of the posterior
cruciate ligament is best detected when a posterior drawer test
is performed with the knee in 90° of flexion. Repeating this test
with the tibia internally rotated will result in a substantial decrease
in the amount of posterior laxity at 60° and 90° of knee flexion.