Observations on sectioned and opened preparations of human sacroiliac joints (SI joints) show the presence of cartilage-covered ridges and depressions, which are complementary on the auricular surfaces. These macroscopically visible features of the joints, which become visible relatively early in life, are more pronounced in men than in women. This type of roughening, as well as that by increased coarseness of the auricular surface, is viewed as a nonpathologic adaptation to the forces exerted at the SI joints, leading to increased stability. Differences between men and women may be attributed to childbearing and to a difference in the center of gravity. It is emphasized that intra-articular ridges and depressions can be misinterpreted roentgenologically as osteophytes.
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