Review Question - QID 217954

This patient's physical examination findings include a reverse lachman, positive posterior sag sign, and positive varus stress at 0° and 30°, which indicate injury to the posterior cruciate ligament (PCL) and lateral collateral ligament (LCL).

A thorough knee ligamentous exam is important in the diagnosis and eventual management of patients with significant knee injuries. Cruciate injuries are evaluated by appreciating the degree of anterior/posterior translation and rotational instability. The anterior cruciate ligament (ACL) is evaluated with the lachman test and the pivot shift. The posterior cruciate ligament (PCL) is evaluated with the reverse lachman, posterior drawer, or posterior sag sign. Collateral ligaments are evaluated with varus (LCL) or valgus (MCL) stresses placed at either 0° or 30°. Laxity at 0° and 30° indicates a concomitant cruciate injury. Posterolateral corner injuries are evaluated with the Dial test, reverse pivot shift test, and the posterolateral drawer.

Lubowitz et al. provides a current concept review in the comprehensive evaluation of knee instability. In the article, they review the different ligamentous injuries that contribute to specific instability patterns. They go into further detail by discussing the anatomy and biomechanics that relate to the ultimate management of the condition.

Wind Jr. et al. discusses the evaluation and treatment of PCL injuries specifically. They note that PCL injuries are still not as well understood as ACL injuries and surgical guidelines/techniques are still not always well agreed upon. In this review they offer a review of current evaluation and treatment of these complex injuries.

Bronstein et al. published a JAAOS review article on the physical examination of knee ligament issues, noting that history and physical examination remain the mainstay in diagnosis, even with advanced imaging techniques available. They describe the proper use of specific tests whic can help guide diagnosis. They also go more in depth on the underlying anatomy and biomechanics which pertain to these tests and how they are performed.

Illustration A demonstrates a clinical photo showing evidence of positive posterior sag sign (left) compared to a normal knee (right)

Incorrect Answers:
Answers 1 & 2: With injury to the PCL, the illusion of ACL injury may be present given the higher degree of anterior-posterior tibial motion; in the setting of a grade 1-2 lachman with a good endpoint and a negative pivot shift, there is a low likelihood of isolated ACL rupture or ACL + PCL rupture.
Answer 3: Positive reverse lachman and posterior sag tests are indicative of PCL injury but the presence of a positive varus stress at 0°/30° would indicate concomitant LCL injury.
Answer 5: With a negative dial sign and negative reverse pivot shift test, it is unlikely there is a complete posterolateral corner injury (LCL, popliteus, popliteofibular ligament), despite isolated involvement of the lateral collateral ligament.