We used an in vitro knee-testing apparatus to measure anterior-posterior
displacement of the tibia on the femur and the accompanying tibial rotation
in response to an applied anterior-posterior force. Testing was performed
on nine intact knees, on five knees after medial meniscectomy, on three
knees after isolated section of the anterior cruciate ligament, and on
eight knees after both excision of the medial meniscus and section of the
anterior cruciate ligament. The induced anterior-posterior displacement and
the coupled rotation were unaffected by meniscectomy. Isolated section of
the anterior cruciate ligament allowed a significant (p less than 0.05)
increase in anterior displacement but had no effect on posterior
displacement. The coupled internal rotation associated with anterior
displacement was lost after section of the anterior cruciate ligament.
Excision of the medial meniscus and section of the anterior cruciate
ligament allowed significantly (p less than 0.05) greater increases in
anterior displacement than those already increased by isolated section of
the anterior cruciate ligament.