Novel Methods for Diagnosis and Treatment of Posterolateral Rotatory Instability of the Knee

Abstract

Injury to the posterolateral corner structures of the knee can cause posterolateral rotatory instability, a condition that has attracted increased attention over recent years1. This injury is often associated with cruciate ligament injury, and its diagnosis can be difficult unless one has a high degree of clinical suspicion for an injury to the posterolateral corner structures2,3. Although a number of treatment methods have been proposed over the past twenty years2,4-12, there has been considerable controversy regarding the optimal method of surgical treatment for this injury. The consequences of missed or unsuccessfully treated posterolateral rotatory instability can be profound: reconstructed anterior or posterior cruciate ligaments can fail, and persistent posterolateral rotatory instability may eventually cause pain, instability, and even degenerative changes13-17. In this report, we describe the use of an external rotation-valgus stress radiograph for the evaluation and diagnosis of posterolateral rotatory instability, and we describe a new anatomical reconstruction procedure involving use of a split Achilles tendon allograft for its treatment. ### Background Although several physical examination techniques for the detection of posterolateral rotatory instability of the knee have been described18,19, no widely accepted method of objective documentation, such as the use of posterior stress radiographs to identify a posterior cruciate ligament injury, has been established for posterolateral rotatory instability. Consequently, assessment of posterolateral rotatory instability is very subjective and dependent on the examiner's experience. Several biomechanical studies have documented that sectioning of the posterolateral corner structures markedly increases external rotation of the tibia at 30° of knee flexion, whereas sectioning of the posterior cruciate ligament alone does not have the same effect20-22. Consequently, increased external rotation of the tibia relative to the femur at 30° of knee …