We performed biomechanical stress tests preoperatively on the knees of
fifty-one patients with an injury to the knee. We measured the amount of
anterior and posterior tibial translation at 90 degrees of knee flexion
using a roentgenographic technique and a fifty-newton joint load. Knees
with an isolated meniscal tear exhibited no abnormal motion. There was no
difference in motion of the knee between patients with a rupture of the
anterior cruciate ligament and patients with this injury who had had a
prior medial meniscectomy. We found that prior knee surgery that was not
associated with stability did not adversely affect the test procedure. A
significant finding, however, was that only nineteen of twenty-five
patients with a ruptured anterior cruciate ligament had greater excursion
on the injured side compared with the uninjured knee. Because of this
inconsistent result, a biomechanical stress test at 90 degrees of knee
flexion measuring anterior and posterior translation under a fifty-newton
joint load appears insufficient in itself to be of clinical use.