The relation between biomechanical and psychological factors in patients with low-back pain.

Behavioral factors are increasingly being recognized for their role in determining the course and outcome of low-back disorders. This paper examines the relation between behavioral variables, which include psychological symptoms and pain tolerance, and biomechanical variables. The majority of the 89 patients tested could be classified into two groups. One group was intolerant of pain and showed reduced spinal mobility, restricted straight leg raising, and altered flexor-extensor muscle balance. The other group was more tolerant of pain and did not show restriction of motion or muscle imbalance. Spinal mobility was also related to psychological symptoms. A model is proposed which points to a feedback between spinal motion and the patient's ability to cope with pain as one mechanism that determines return to a functional range of motion.