Low back pain (with or without sciatica) is one of the most common complaints of patients in all developed countries (Ackerman et al., 1997a; BenDebba et al., 1997; Deyo & Tsui-Wu, 1987; Fredrickson et al., 1984; Long, 1989; Long et al., 1979). In the USA, it is the second most common reason to see a physician (Carey et al., 1995), and the most common reason for Workmen's Compensation claims (Long et al., 1996). Surgery on the spine now ranks third among procedures in the Medicare population (Zeidman & Long, 1996).

Thus, it is surprising to discover that there is no complete classification system for low back pain with or without sciatica, and standards for diagnosis, treatment, and assessment of outcomes of therapy have not been established (BenDebba et al., 1997; Merskey & Bogduk, 1994).

One of the principal reasons why this situation exists is that for most patients, the causes of low back pain remain unknown, and the value of therapy is uncertain (Bigos et al., 1994; Waddell et al., 1984). The magnitude of the problem and the huge expenditures required for low back pain make it particularly important to understand what is currently known and not known about back pain, so that treatment is rational and based upon the most up-to-date information and guidelines.

Classification of low back pain

Classifications may be etiologic, based upon anatomical descriptions, or may use surrogate descriptors when anatomical and pathological details are not well understood. The most common classification system for low back pain is temporal and relates to descriptions of patients, rather than to pathological processes (BenDebba, 1997; Bigos et al., 1994; Long et al., 1996). This practical system is of real value in managing patients, although it does not provide the desired etiologic accuracy that is available with anatomical and pathological classifications (Bogduk, 1997; Main et al., 1992).

Transient low back pain

Transient low back pain is that which occurs so briefly that the patient does not seek medical attention. The etiologies of these brief periods of low back pain remain unknown, but will be discussed in greater detail later in the chapter.

Acute low back pain

Acute low back pain lasts for a longer period of time, usually a few days, and often brings the patient to medical attention.