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Black line sign

Last revised by Dr Joachim Feger on 01 Sep 2021

The black line sign refers to a linear finding of the articular cartilage on magnetic resonance imaging initially seen in the trochlear groove 1-3.

These lesions have been found also in all other regions of articular cartilage in the knee and not only on T2 weighted images but also in other sequences e.g. fat-suppressed proton density-weighted images 4.

Correlation of those findings with arthroscopy showed that a significant number of dark articular lesions linear or non-linear in nature correspond to areas of cartilage degeneration 4.

Therefore it has been suggested that the black line sign or focal areas of low signal intensity within healthy cartilage indicate areas of ‘fissuring’ or ’cartilage degeneration’ 1-4

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