The term traumatic arthritis is commonly applied to joints which have been involved in an acute direct trauma, trauma secondary to fracture or trauma secondary to dislocations, particularly recurring dislocations. The term conveys a purely clinical picture since none of these conditions justifies removal of hyaline cartilage for histologic study. This statement is true with one exception only, that of recurring sacroiliac strain. In arthrodesis of the sacro-iliac joint for relief of recurring strain, an ideal opportunity offers itself for histologic study of hyaline cartilage repeatedly exposed to trauma. The type of trauma involved is abnormal pressure resulting from disalinement of irregular, normally congruous surfaces. By such disalinement, prominences become apposed and consequently exposed to abnormal pressure (figs. 1 and 2).
In order to determine the appearance of surfaces of the normal sacroiliac joints, sections were obtained from autopsies on persons without a history of sacro-iliac disorder. Photomicrographs of these