The Only Thing to Fear Is Fear of Low Back Pain Itself
In patients with low back pain, fear is a bad thing. Doctors know that patients who are especially afraid of their back pain tend to have a harder time getting better.

In this study, researchers were trying to find a way to predict which patients would have the hardest time going back to work. Their study group was patients who had low back pain that occurred on the job. The only factor that really predicted which patients would have a hard time was--you guessed it--fear. The workers who were most afraid that their jobs would cause them back pain were also the most likely to be on sick leave four weeks after their injury. 

The researchers used a specific type of survey called the Fear-Avoidance Beliefs Questionnaire to rate patients' fear. They suggest that this survey could help doctors target which patients might need more help getting over their fear--and getting back to work.
References
Julie M. Fritz, PT, PhD, ATC, and Steven Z. George, PT, MS. Identifying Psychosocial Variables in Patients with Acute Work-Related Low Back Pain: The Importance of Fear-Avoidance Beliefs. In Physical Therapy. October 2002. Vol. 82. No. 10. Pp. 973-983.