The thermographic pattern of the lower back with special reference to the sacro-iliac joints in health and inflammation.

The thermographic appearance of the sacro-iliac joints in health and in active inflammation has been established on the basis of 72 thermographic examinations of healthy volunteers and 82 examinations of patients with clinically and radiographically active disease. In the latter group a certain number of cases showed increased heat over the sacro-iliac joints. In addition to the heat patterns described, the main conclusion of the study is a certain variability of the normal thermal pattern, a basic experience of which is necessary for the optimal interpretation of a thermogram in suspected sacro-iliitis. Despite this variability, it is possible to recognize a standard heat pattern from which most heat patterns can be derived with more or less quantitative variations. One factor affecting the thermal pattern in a fairly constant way is the amount of subcutaneous fat.