Disclosures: David J. Park, MD: No financial relationships or conflicts of interest

Case Diagnosis: A 60-year-old female skier with left lateral mechanical knee pain and inconclusive MRI presents to sports medicine clinic for diagnostic ultrasound and found to have lateral meniscal extrusion, prompting arthroscopy and eventual diagnosis and repair of lateral meniscal root tear.

Case Description: A 60-year-old woman was referred by orthopedics for diagnostic ultrasound of her left knee. While skiing in deep powder, her left ski deviated laterally and forced external rotation of her leg with an associated loud pop. She noted ongoing sharp pain over the lateral knee with a pop when transitioning from a loaded squat position. On examination, meniscal testing was negative. Dynamic loading of the joint with a squat provoked index pain with an audible clunk at 45 degrees of flexion. Magnetic resonance imaging (MRI) showed increased degenerative signal within the lateral meniscus. Ultrasound of the lateral meniscus demonstrated hypoechoic linear signal and extrusion of the posterolateral portion. Dynamic ultrasound was performed with a loaded squat and demonstrated subluxation of the extruded meniscal portion with flexion and return of the extruded meniscus with knee extension, corresponding with her painful clunk.

Setting: Sports medicine clinicAssessment/

Results: Findings were discussed with orthopedics who recommended arthroscopy. Intraoperatively she was found to have a complete lateral meniscal posterior root tear which was repaired surgically. She gradually progressed to full activity without pain or popping and repeat ultrasound after 5 months showed resolution of her lateral meniscal subluxation.

Discussion: Meniscal root tears are associated with meniscal extrusion and cause increased joint forces. Due to the risk of degenerative joint changes, surgical repair is favored. Ultrasound can diagnose meniscal tears with >85% sensitivity and specificity and can be used dynamically to assess for stability.

Conclusion: This case highlights the utility of dynamic ultrasound directly impacting surgical decision making to proceed with arthroscopy when MRI was unable to adequately explain symptoms.

Level of Evidence: Level V

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/lateral-meniscal-root-tear-with-lateral-meniscal-extrusion-diagnosed-with-dynamic-ultrasound/