REIDER PART 273

Chaptkr 6_Knee 233

test,theexamincrgraspsthepatientslegat theankle with both hands (Fig. 6-51 A). The internal rotation, valgus, and flexion forces are applied indirectly at the ankle (Fig. 6-5IB). This usually produces a less violent reduction than the classic pivot shift and is less threatening to the patient with significant abnormal anterior laxity. A good method is to begin with the flexion-rotation drawer test and to proceed to the classic pivot shift technique if the results of the flexion-rotation drawer are equivocal. Losse^#s Test. The Losse test is another technique for demonstrating the pivot shift phenomenon. To perform the Losse test, the examiner stands facing the supine patient from the side of the examination table. To exam-ine the right knee, the examiner’s right hand supports the patients right foot and ankle in an externally rotated position braced against the examiner’s abdomen. The patients knee is then pushed into 30° of flexion to rclax the hamstrings (Fig. 6-52A). The cxamincr s left hand is placed on the knee with the fingers ovcr the patella and the thumb behind the head of the fibula, and a valgus stress is applied (Fig. 6-52B). As the knee is slowly extended, the head of the fibula is pushed forward with the thumb of the left hand, using the fingers placed over the patella to provide countcrprcssurc.

If the test is positive, the latcral tibial plateau is felt to sublux anteriorly as the knee approaches fuli extension

(see Fig. 6-52C). Losse and colleagues emphasized that the patient must identify the subluxation maneuver as his or her chief complaint for the test to be considered positive.

POSTERIOR LAXITY

The next group of tests are those for abnormal posterior laxity of the knee. Rupture of the posterior cruciate ligament (PCL) is necessary for a detectable inerease in straight posterior laxity, although damage to the posterolateral struc-tures further inereases the magnitude of the abnormal posterior laxity.

Laboratory research has shown that sectioning the PCL produces the greatest inerease in posterior laxity when the knee is flexed between 70° and 90°. Thercfore, the most sensitive way to test for PCL injury is with the knee flexed between 70° and 90°.

Posterior Drawer Test. The most basie test for PCL injury is the posterior drawer test. The starting position is essentially the same as that for the anterior drawer test; the patienfs knee is flexed 90° and the foot stabilized. In a patient with a torn PCL, a dropback phenomenon usually occurs in this position: gravity causes the tibia to sub-lux posteriorly with rcspect to the femur, resulting in an abnormal appearancc that is best appreciated when both knees are viewed in profile (Fig. 6-53). When such a dropback phenomenon occurs, the tibial tubercle appears