The posterolateral drawer test and external rotational recurvatum test for posterolateral rotatory instability of the knee.

Posterolateral drawer tests and external rotational recurvatum tests are used to detect posterolateral rotatory instability. A specific manner of performance of these tests is necessary to properly interpret the nature of acute and chronic knee conditions. The posterolateral drawer test is performed at 80 degrees of knee flexion and is maximum in 15 degrees of external rotation. Since the posterior cruciate ligament is intact in posterolateral rotatory instability, the posterior drawer will be negative on maximum internal tibial rotation. Fibrous scar tissue may conceal an otherwise positive posterolateral drawer sign in the chronic condition. The external rotational recurvatum test examines the knee in extension. Tightness and spasm of the biceps femoris and semimembranosus may obscure a positive external rotational recurvatum test in the acute or chronic condition. The external rotational recurvatum test will be negative when the anteromedial and intermediate bundles of the anterior cruciate ligament are intact owing to their contact with the intercondylar shelf in extension. The posterolateral drawer and the external rotational recurvatum can be subtle tests and require careful observation for accurate evaluation of both the acute or chronic condition of the knee joint.