Consider the Tidemark: Figure 1.

Abstract

As the most conspicuous histologic feature of normal adult articular cartilage, the tidemark begs for our understanding. In their original description, Fawns and Landells likened this landmark to the irregular line of debris that is left on a sandy beach by the high point of a now-receding tide1 (Figure 1A). Such tidemarks comprise a mixture of marine flotsam, and so contain a variety of stuff from the sea. If the tidemark of cartilage is aptly named, as I believe it to be, it too should be a passive deposit of debris, but what are its constituents and where do they come from? Figure 1. A. A tidemark on the beach at Manzanita, Oregon, USA. B. Mallory aniline blue stain of the tidemark in a normal human metacarpal phalangeal (MCP) joint. Note that cell nuclei and the tidemark share orange staining not seen in the matrix. This image, as well as those that follow, was from an older subject without known rheumatic disease whose body was donated for anatomic study through the willed body program at the University of Washington. C and D. Von Gieson stains of first phalanx base and metacarpal head from 1 MCP joint. The trilaminar structure seen here was stressed by Lyons, et al 10. Its basis remains unexplained. The tidemark duplication seen in the metacarpal head is generally considered to be evidence of osteoarthritis. E. Mowat stain. Granularity of the tidemark (? apoptotic bodies) was described in the classic report of Fawns and Landells1. F. Masson trichrome stain. Again note that, as in all sections, … Address correspondence to Dr. P.A. Simkin, Division of Rheumatology, Box 356428, Department of Medicine, University of Washington, Seattle, Washington 98195, USA. E-mail: psimkin{at}uw.edu