Normal and degenerating articular cartilage: in vitro correlation of MR imaging and histologic findings.

Histologic correlation of the different magnetic resonance (MR) appearances of articular cartilage has not been studied extensively. Therefore, the authors correlated thin (high-resolution) MR sections of articular cartilage with histologic sections. Human cadaver lumbar facet joints were imaged with a 1-mm section thickness and a 4-cm field of view, then sectioned and stained for histologic comparison. MR imaging patterns were identified that correlated with normal cartilage and three histologically different patterns of degeneration.

Articular cartilage: correlation of histologic zones with signal intensity at MR imaging.

Zones of high and low signal intensity on magnetic resonance (MR) images of articular cartilage were correlated with the four histologic zones normally found in such cartilage. Grossly normal articular cartilage from knees and ankles of a fresh cadaver were used in the study. The three zones identified on MR images included a low-intensity zone near the articular surface, a zone of higher signal intensity next to that, and a second zone of low intensity that was deep to the two others. The location of the superficial low-intensity zone corresponded to dense, tangentially oriented layers of collagen in the superficial histologic zone. Higher signal intensity deep to the superficial low-intensity zone correlated with cartilage in the transitional zone. The deep low-intensity zone correlated with a combination of deep radiate and calcified cartilage and cortical bone. Results of this study indicate that, with high resolution, MR imaging may demonstrate three zones of differing signal intensity in articular cartilage. The superficial low-intensity zone may be a useful marker of the surface of normal articular cartilage.