The cartilage black line sign: an unexpected MRI appearance of deep cartilage fissuring in three patients

Abstract

Many patterns of cartilage signal anomalies have been described in the knee since the advent of magnetic resonance imaging (MRI). With the now widespread use of preoperative MRI, some of these anomalies have proven to represent true pathology, while others have been shown to be normal variants or artifacts at arthroscopy. We describe three patients with an MR cartilage abnormality, not previously illustrated in the literature, consisting of a thin dark signal line on T2-weighted imaging, oriented perpendicular to the plane of imaging. This aberration proved to represent a deep cartilage cleft at arthroscopy (two patients) and at CT arthrography (one patient). Such full thickness fissures are generally considered to have the opposite appearance, that of fluid signal intensity on T2-weighted images.

The Clinical Significance of Dark Cartilage Lesions Identified on MRI

“…Our study expands on the work of Stephens and associates [13] and Wissman and associates [16,21], who investigated linear dark cartilage lesions in the central femoral trochlea, termed the cartilage black line sign. Wissman and associates defined this linear dark cartilage lesion as measuring less than 2 mm in thickness and two or more slices in length and extending through the entire thickness of the cartilage.…”

“…Stephens and associates [13] recently identified what has been termed the "cartilage black line" sign of the central femoral trochlea of the knee. This lesion was defined as linear low signal intensity on T2-weighted images oriented perpendicular to the subchondral bone and located in an area of the cartilage that was morphologically normal on MRI and was found to correlate with cartilage fissuring at arthroscopy.…”

“…Stephens and associates [13] found that both of two patients with a cartilage black line sign showed evidence of cartilage degeneration at arthroscopy, whereas Wissman and associates [16] found that one of eight patients showed evidence of cartilage degeneration at arthroscopy. We have improved on the arthroscopic correlation sample size of these studies, and our findings more strongly support an association with cartilage degeneration, with 17 of 27 lesions (63.0%) corresponding to cartilage degeneration at ar-throscopy.…”

“…Most investigators have reported an increase in the T2 relaxation time and increased signal intensity on T2-weighted images of degenerative cartilage, attributed to multiple factors including increased water content, decreased macromolecular content, and disruption of collagen matrix ultrastructure [9][10][11][12]. Conversely, in vitro and in vivo studies have also shown that cartilage degeneration may be associated with a decrease in T2 relaxation time and decreased signal intensity on T2-weighted images [13][14][15][16][17][18][19], which may be due to factors such as magnetization transfer and disruption of tissue anisotropy [20]. However, the presence of low signal intensity in cartilage is not widely…”

Diz Eklemi: Kikirdak

“…Kıkırdak içerisinde sıvı sinyalinde lineer bölgeler fissü-rü yansıtırken geniş alanlar kıkırdak kaybını gösterir. Küçük hasta serisi olan bir çalışmada fokal düşük T2 sinyalli lezyonların da sıklıkla fissür ile ilşkili olduğu gösterilmiştir [9]. Parsiyel volüm artefaktı kıkırdak görüntülemede komşu yağ veya sıvı sinyali ile lezyonların ayrımında sorun yaratabilir.…”