What causes Double Delta Sign in knee on MRI?
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Answer:
Anteriorly displaced bucket-handle tear fragment of the lateral meniscus situated posterior to the anterior horn, seen in bucket-handle tears of the lateral meniscus which clinically present with knee pain, swelling, and limited mobility, typically due to trauma or degenerative processes.
Why is it called so?
Named for the appearance of two adjacent triangular shapes resembling deltas (ฮฮ) on sagittal MRI, with the anterior triangle representing the normal anterior horn and the posterior triangle the displaced meniscal fragment. This characteristic appearance is described as the Double Delta Sign.
Pathophysiology
In a bucket-handle tear, a full-thickness vertical longitudinal tear of the meniscus allows the inner fragment to displace anteriorly into the anterior intercondylar notch or posterior to the anterior horn; on sagittal MRI, this fragment lies adjacent to the intact anterior horn, creating two distinct triangular low-signal structures mimicking double anterior horns, producing the Double Delta Sign.
Alternative names: Double anterior horn sign
Other associated named signs: Double ACL sign, fragment in notch sign, flipped meniscus sign
Access all radiology signs posted so far: https://radiogyan.com/radiology-signs/
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