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Review
. 2024 Dec 31;12(1):e70126.
doi: 10.1002/jeo2.70126. eCollection 2025 Jan.

Meniscal extrusion: Proposal for a novel qualitative classification

Simone Perelli  1   2 , Pietro Conte  1   3   4 , Nicola Pizza  1 , Rodolfo Morales-Avalos  5 , Elizaveta Kon  3   4 , Alberto Grassi  6 , Stefano Zaffagnini  6 , Joan Carles Monllau  1   2
Affiliations
Review

Meniscal extrusion: Proposal for a novel qualitative classification

Simone Perelli et al. J Exp Orthop. .

Abstract

Meniscal extrusion (ME), defined as the radial displacement of the meniscal body outside the margins of the tibial plateau, has been seen as an independent and relevant predictor of intra-articular knee degeneration. Nonetheless, available classifications for ME are exclusively quantitative assessments not considering the context in which extrusion is identified. Indeed, ME can be the result of several different conditions spanning from acute tears to chronic degeneration and its definition cannot be only dependent on the numeric calculation of the radial displacement of the meniscal body. Furthermore, growing evidence supports the existence of a paraphysiological ME resulting from joint loading, limb malalignment, anatomical abnormalities of the meniscal attachments to the femur and tibia or a nonpathological finding after meniscal allograft transplantation. It is therefore clear that an exclusively quantitative assessment of ME cannot be sufficient since this condition can develop in such different clinical scenarios. For this reason, a novel qualitative classification for ME is proposed, differentiating between three distinct conditions: a paraphysiological ME, a pathological ME and ME related to degenerative conditions. Furthermore, a comprehensive review of the present literature has been conducted to report the most relevant and updated evidence on the topic highlighting the difference in the clinical management of each different category.

Level of evidence: Not applicable.

Keywords: degenerative; extrusion; knee; meniscal extrusion; meniscus; osteoarthritis.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
MRI coronal view of a right knee showing a paraphysiological meniscal extrusion. The MRI was performed for patellofemoral pathology and medial meniscal extrusion was detected in an asymptomatic medial compartment. The abnormality of the meniscotibial ligament at this level was detected. MRI, magnetic resonance imaging.
Figure 2
Figure 2
MRI coronal view of a right knee at 5 years follow‐up post lateral meniscal transplantation. An almost complete meniscal body extrusion can be observed. Despite this radiological finding the patient is completely asymptomatic. MRI, magnetic resonance imaging.
Figure 3
Figure 3
MRI coronal view of a left knee. Posterior medial root tear lesion associated with meniscal extrusion. MRI, magnetic resonance imaging.
Figure 4
Figure 4
(a) MRI coronal view of a left knee. The red‐dotted lines represent the amount of meniscal extrusion. (b) intraoperative arthroscopic view of the radial lateral meniscal lesion, the red and black asterisk pointed out the two meniscal segments. MRI, magnetic resonance imaging.
Figure 5
Figure 5
MRI coronal view of a right knee. Patient with valgus instability due to a medial collateral ligament grade 3 lesion 6 months before. In the MRI are visible both the scarred medial collateral ligament at the femoral insertion and the lesion of the meniscotibial ligament with concomitant extrusion. MRI, magnetic resonance imaging.
Figure 6
Figure 6
MRI coronal view of a right knee. Medial ME as well as signs of medial meniscal degeneration can be observed. A mild reduction of tibial chondral thickness is visible without subchondral changes nor osteophytes. ME, meniscal extrusion; MRI, magnetic resonance imaging.
See this image and copyright information in PMC

References

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