Combined PCL instabilities cannot be identified using posterior stress radiographs in external or internal rotation: A cadaveric study.

Purpose: Posterior stress radiography is recommended to identify isolated or combined posterior cruciate ligament (PCL) deficiencies. The posterior drawer in internal (IR) or external rotation (ER) helps to differentiate between these combined instabilities. The purpose of this study was to evaluate posterior stress radiography (PSR) in isolated and combined PCL deficiency with IR and ER compared to PSR in neutral rotation (NR) for diagnosing combined PCL instabilities.