Assessment of Laxity in Multiligamentous Knee Injuries Using Stress Radiographs: A Simple Technique for a Busy Clinic

Background: Multiligamentous knee injuries are complex, with highly individualized treatment plans based on patient and injury-specific factors. Stress radiographs are an important tool for objectively quantifying knee laxity; however, they are often not formally taught during clinical training. Purpose: To provide a reproducible method for obtaining stress radiographs. Indications: Stress knee radiographs are used in the setting of acute and chronic knee ligamentous and soft tissue injury. Technique Description: Coronal laxity: Knees are flexed at 20°, the x-ray beam is tilted 20° cephalad, and aligned with the inferior pole of the patella. Apply a valgus force with slight external rotation to the knee to test the medial collateral ligament (MCL). Perform on the contralateral knee. Use a varus force to test the lateral collateral ligament (LCL) and the posterolateral corner. Measure the joint space width with the LaPrade method. Sagittal laxity: Position the patient supine and flex the knee to 80°. The patient holds the cassette parallel to the x-ray beam, which is at the foot of the bed. Allow the tibia to sag without support, and compare the side-to-side difference on the bilateral radiograph. Results: The case in this video shows a side-to-side difference, suggesting a grade 3 MCL, LCL, and partial posterior cruciate ligament injury. Discussion/Conclusion: Stress radiographs support accurate diagnosis of complex knee injuries and provide an objective measure of knee stability. These techniques can be performed in an ambulatory clinic setting and are cost-effective, efficient, and support clinical decision-making in the treatment of complex knee injuries. Patient Consent Disclosure Statement: The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.