The purpose of the study was to examine how the psychological reactions to pain of acute low back pain (LBP) patients would compare to the psychological reactions to pain of chronic LBP patients who displayed signs and symptoms which were either congruent or incongruent with underlying anatomy and physiology. It was also of interest to examine whether negative cognitive and affective variables would mediate the expression of pain in these pain groups, and whether verbal and nonverbal facial

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... ures of pain could be used to discriminate among pain groups. Subjects were assigned to the acute pain group if they had recurring or persistent pain for less than a three month period, and to the chronic pain group if they had recurring or persistent pain for longer than a three month period. The Pain Drawing (Ransford, Cairns & Mooney, 1976), the Nonorganic Physical Signs Assessment (Waddell, McCulloch, Kummell & Venner, 1980) and the Inappropriate Symptom Inventory (Waddell, Main, Morris, Di Paolo & Gray, 1984) were used to assign chronic pain patients to either the congruent or incongruent chronic LBP group. A physiotherapy protocol in which patients were asked to genuinely express pain, exaggerate and mask pain in response to a painful range of motion task was used to obtain a wide range of facial behaviour that would likely be relevant to understanding the expression of pain in these patient populations. Verbal reports of pain in response to the painful range of motion task, and in response to the pain that patients experienced on a daily basis were also examined. In addition, questionnaires concerned with coping strategies, worry and emotionality were used to tap cognitive and affective components of pain. Several demographic and patient pain related variables (e.g., medication use, disability, physical impairment) were also collected. The results of the study suggested that the acute and chronic incongruent pain patients had a similar psychological reaction to pain that was greater than the psycholog [...]