Structural periodicity in human articular cartilage: comparison between magnetic resonance imaging and histological findings

Objective: To relate the vertical striations visualized in the deeper layer s of articular cartilage by Magnetic Resonance Imaging (MRI) to histologica l features. Methods: Two knee joints recovered at post-mortem from males in their seven ties with no history or visual evidence of joint disease were examined. MR images were obtained in a 4.7 T 400 mm-bore magnet, after which the knees w ere fixed, sectioned, and examined histologically. Results: High resolution MR showed vertical high/low signal striations with a two to three-fold variation in signal intensity and a periodicity of 0.5 6 (+/- 0.16 mm), most prominent in weight bearing areas. Histological secti ons revealed alternating light and dark staining areas with a periodicity o f 1.01 +/- 0.54 mm in the lower zones of the cartilage, some, but not all o f which clearly represented folding. Given that MR will only visualize vert ical structures in cartilage aligned at 90 degrees, whereas histology will cut them at varying angles, it is likely that the vertical structures seen by each modality correspond, and that they represent structural heterogenei ty in cartilage; perhaps the presence of plates of high collagen and proteo glycan content. Conclusion: The vertical striations seen routinely in the deep zones of hya line articular cartilage on histological sections are not artefactual; they are likely to represent structural heterogeneity due to the presence of ar eas of high collagen and high proteoglycan content that exist in weight-bea ring areas. This structural heterogeneity may be of great importance to the integrity and function of the cartilage. (C) 1999 OsteoArthritis Research Society International.