title: The trochlear cleft: the “black line” of the trochlear trough.
abstract: The “cartilage black line sign” is a recently described T2 dark cartilage lesion that we have identified appearing as a cleft in the trochlear trough. The purpose of our study was to define the MR imaging characteristics of a trochlear cleft, determine its incidence, and correlate the MR findings with arthroscopy.
  
  
  
  A total of 1,300 consecutive MR examinations of the knee were retrospectively reviewed by consensus of two fellowship-trained musculoskeletal radiologists. The MR imaging characteristics and location of a trochlear cleft were determined. Imaging results were compared to arthroscopy when available. Patient age and gender were compared to 25 randomly selected control patients without trochlear clefts.
  
  
  
  A total of 25 (1.9%) individuals (11 females and 14 males; age range 19–45 years; mean age 28 years) were diagnosed with a trochlear cleft. The control group consisted of 11 females and 14 males; age range 19–83 years; mean age 46 years. Mean cleft length was 7 mm (range 6–12 mm); cleft location was consistently in the lower trochlear trough. No full-thickness cartilage defects were identified in the eight individuals in whom arthroscopic correlation was available. A grade 2 cartilage lesion was identified in a single individual; another progressed from grade 0 to a full-thickness trochlear lesion over an 8-month interval. Eight individuals were athletes. No significant difference in gender was noted between the two groups, however, the study group was significantly younger p<0.0001.
  
  
  
  A trochlear cleft is a rare finding in young active individuals. It most likely indicates an incomplete cartilage fissure which may rarely progress to a full-thickness defect.
authors: Department of Radiology, University of Cincinnati Medical Center, Cincinnati, OH 45267-0761, USA. robert.wissman@uchealth.com
authors: Robert D
authors: RD
authors: Wissman
authors: Jerrell
authors: J
authors: Ingalls
authors: Joshua
authors: J
authors: Nepute
authors: Nathaniel
authors: N
authors: Von Fischer
authors: Rupa
authors: R
authors: Radhakrishnan
authors: Daniel
authors: D
authors: Hendry
authors: Keith
authors: K
authors: Kenter
mesh_terms: D000328:Adult; D002358:Cartilage, Articular / Q000002:abnormalities* / Q000473:pathology*; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000002:abnormalities* / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055815:Young Adult