Absent bow tie sign (knee)

Last revised by Frank Gaillard ◉ ◈ on 6 Sep 2022

Citation, DOI, disclosures and article data

Citation:

Gaillard F, El-Feky M, Bell D, et al. Absent bow tie sign (knee). Reference article, Radiopaedia.org (Accessed on 02 Oct 2023) https://doi.org/10.53347/rID-7218

DOI:

https://doi.org/10.53347/rID-7218

Permalink:

https://radiopaedia.org/articles/7218

rID:

7218

Article created:

17 Sep 2009, Frank Gaillard ◉ ◈

Disclosures:

At the time the article was created Frank Gaillard had no recorded disclosures.

View Frank Gaillard's current disclosures

Last revised:

6 Sep 2022, Frank Gaillard ◉ ◈

Disclosures:

At the time the article was last revised Frank Gaillard had the following disclosures:

Radiopaedia Australia Pty Ltd and Radiopaedia Events Pty Ltd, Director, Founder and CEO (Radiopaedia) (ongoing)
Biogen Australia Pty Ltd, Investigator-Initiated Research Grant for CAD software in multiple sclerosis: finished Oct 2021 (past)

These were assessed during peer review and were determined to not be relevant to the changes that were made.

View Frank Gaillard's current disclosures

Revisions:

21 times, by 11 contributors - see full revision history and disclosures

Systems:

Musculoskeletal

Sections:

Signs

Tags:

knee

Synonyms:

Absent bow tie sign in knee

The absent bow tie sign represents the loss of the normal appearance of the menisci on parasagittal MRI images and is suggestive of meniscal injury.

Normally the medial and lateral menisci appear as low signal triangular structures linked by a thin body located between the femoral condyles and tibial plateau. The appearance of the menisci has been likened to a bow tie.

As the normal meniscus laterally measures 9-12 mm in width, it should be seen on a number of adjacent images (2-3 images if imaged with 3 mm thick slices with a 1 mm skip).

An absent bow tie sign is therefore when less than two sagittal slices demonstrate a normal body of the meniscus and is suggestive of meniscal pathology, including:

bucket handle tear with displacement (often with a double PCL sign)
flap tear with displacement (i.e. bucket handle, but the handle at one end has come loose)
free fragment with displacement (i.e. bucket handle, but the handle at both ends has come loose)

Other meniscal changes can, however, appear similar, including:

prior resection of a meniscal tear
degenerative maceration of the inner edge of the meniscus
small patients (children / small adults)

Related pathology

In contrast, if there are more 2 or 3 sagittal images with a visible bow-tie this implies a discoid meniscus; obviously, this depends on the slice thickness and skip width.