No dynamic extrusion of the medial meniscus in ultrasound examination in patients with confirmed root tear lesion

  • Katrin Karpinski
  • Theresa Diermeier
  • Lukas Willinger
  • Andreas B. Imhoff
  • Andrea Achtnich
  • Wolf PetersenEmail author



Extrusion of the medial meniscus evaluated on magnetic resonance imaging (MRI) has been described as indirect radiological sign for meniscus root tears. However, ultrasound detectable dynamic extrusion is observed in normal physiological settings. The aim of the present study was to analyze the dynamic meniscal extrusion using ultrasound (US) examination in patients with MRI-confirmed meniscal root tears. The hypothesis was that dynamic meniscus extrusion is reduced in patients with medial root tear but not in the healthy meniscus.


Twenty-five patients with a medial root lesion of the meniscus (group I) and 25 healthy controls (group II) were enrolled in this study. The medial meniscus extrusion (MME) of the index knee was determined using ultrasound (US) in supine position and under full weight bearing. Standard knee MRI was used for determining whether the patients were eligible for this study according to the inclusion and exclusion criteria, respectively.


In group I, the mean MME was 3.6 mm (± 1.0 mm) in supine position and 3.7 mm (± 0.9 mm) under full weight bearing according to US measurements. The mean Δ-extrusion was 0.1 mm (± 0.2 mm) and the ratio was 1.0 (± 0.1). Mean medial meniscus extrusion on MRI was 3.9 mm (± 0.9 mm). In group II, mean MME was 1.3 mm (± 0.3 mm) in supine position (US) and 2.3 mm (± 0.4 mm) under full weight bearing (US). The mean Δ-extrusion was 1.0 mm (± 0.4 mm) and the extrusion ratio was 1.8 (± 0.4). In this group, mean extrusion in MRI was 1.4 mm (± 0.7 mm). The difference in mean ultrasound Δ-extrusion, ratio, and MRI extrusion between both groups was statistically significant (p < 0.001).


Based on the results of dynamic ultrasound examination of the medial meniscus, medial root tear leads to significantly decreased dynamic medial displacement of the meniscus compared to healthy meniscus status. The absence of dynamic meniscus extrusion may be an indicator for medial meniscus root injury and could be detected using ultrasound (“dead meniscus sign”).

Level of evidence



Dynamic meniscal extrusion Root tear Ultrasound Meniscal extrusion Dynamic extrusion Magnetic resonance imaging 



No external funding was used.

Compliance with ethical standards

Conflict of interest

All other authors declare that they have no conflict of interest related to this study.

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Informed consent

Informed consent was obtained from all individual participants included in the study.


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Copyright information

© European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA) 2019

Authors and Affiliations

  1. 1.Klinik für Orthopädie und UnfallchirurgieMartin Luther KrankenhausBerlinGermany
  2. 2.Abteilung und Poliklinik für SportorthopädieKlinikum rechts der Isar der Technischen Universität MünchenMunichGermany

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