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

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.

To provide a reproducible method for obtaining stress radiographs.

Stress knee radiographs are used in the setting of acute and chronic knee ligamentous and soft tissue injury.

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.

The case in this video shows a side-to-side difference, suggesting a grade 3 MCL, LCL, and partial posterior cruciate ligament injury.

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.

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