The Distribution of Ochronosis in Osteoarthritic Articular Cartilage in a Knee

Ochronotic Chondropathy: A Case Report

“…Furthermore, though the pigmentation that is characteristic of ochronosis is often described as a "polymer," the notion that these structures are produced by the association of multiple identical monomers (i.e., by homopolymerization) has been contested, and it has been noted that nonpolymeric structures can also produce dark pigmentation similar to ochronosis [37]. Vigorita et al collected and stained samples of intact articular cartilage from a 73-yearold woman who underwent total knee replacement secondary to advanced ochronosis, leading to some of the most striking images of advanced ochronotic pigmentation taken from a human being collected to date [41]. In their report, blanket pigmentation was observed in both the radial and transitional zones, though it was most prominent in the radial zone where it appeared both intracellularly in chondrocytes and within the ECM, while pigmentation was absent in the superficial zone and calcified zone except for some relatively minor pericellular pigmentation in the calcified zone [41].…”

“…Vigorita et al collected and stained samples of intact articular cartilage from a 73-yearold woman who underwent total knee replacement secondary to advanced ochronosis, leading to some of the most striking images of advanced ochronotic pigmentation taken from a human being collected to date [41]. In their report, blanket pigmentation was observed in both the radial and transitional zones, though it was most prominent in the radial zone where it appeared both intracellularly in chondrocytes and within the ECM, while pigmentation was absent in the superficial zone and calcified zone except for some relatively minor pericellular pigmentation in the calcified zone [41]. Based on these results, they hypothesized that (1) the avascularity of cartilage generally disallows the clearing of HGA prior to polymerization and therefore facilitates the deposition of the ochronotic pigment; (2) the movement of water between the superficial zone and the synovial fluid clears HGA, accounting for the relative lack of pigmentation in the superficial zone; and (3) the relatively low metabolic activity and turnover rate of chondrocytes in the calcified zone lead to a low production rate of HGA, thus accounting for the relative lack of pigmentation compared to the radial and transitional zones in advanced ochronotic cartilage [41].…”