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The trochlear cleft: the “black line” of the trochlear trough
Robert D Wissman1, Jerrell Ingalls, Joshua Nepute
1Department of Radiology, University of Cincinnati Medical Center, Cincinnati, OH 45267-0761, USA. robert.wissman@uchealth.com
Skeletal Radiology
|June 29, 2012
Summary
The "cartilage black line sign" or trochlear cleft is a rare T2 dark cartilage lesion found in young athletes. This finding often represents an incomplete cartilage fissure, with rare progression to full-thickness defects.
Area of Science:
- Orthopedics
- Radiology
- Sports Medicine
Background:
- The "cartilage black line sign" is a newly identified T2 dark cartilage lesion.
- This lesion appears as a cleft within the trochlear trough of the knee.
Purpose of the Study:
- To define the MR imaging characteristics of trochlear clefts.
- To determine the incidence of trochlear clefts.
- To correlate MR findings with arthroscopic results.
Main Methods:
- Retrospective review of 1,300 knee MR examinations by two musculoskeletal radiologists.
- Analysis of MR imaging characteristics and location of trochlear clefts.
- Comparison of MR findings with arthroscopy and demographic data of control patients.
Main Results:
- A trochlear cleft was identified in 25 individuals (1.9%), predominantly young athletes (mean age 28).
- Clefts were consistently located in the lower trochlear trough, with a mean length of 7 mm.
- Arthroscopic correlation revealed no full-thickness defects in most cases, though one case showed progression over 8 months.
Conclusions:
- Trochlear clefts are rare findings in young, active individuals.
- This lesion likely represents an incomplete cartilage fissure.
- Progression to a full-thickness defect is uncommon but possible.
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