© 2001 Blackwell Science Inc., 1530-7085/01/$15.00 Pain Practice, Volume 1, Number 3, 2001 255–273 Pain Generators of the Lumbar Spine Phillip S. Sizer Jr., MEd, PT*; Valerie Phelps, PT † ; Omer Matthijs, PT ‡ *Texas Tech University Health Science Center, School of Allied Health, Physical Therapy Program, Lubbock, Texas; † International Academy of Orthopedic Medicine, US, Tucson, Arizona; ‡ International Academy of Orthopedic Medicine, Europe, Schoten, Belgium  Abstract Different anatomical structures and pathophysi- ological functions can be responsible for lumbar pain, each producing a distinctive clinical profile. Pain can arise from the intervertebral disc, either acutely as a primary disc related dis- order, or as result of the degradation associated with chronic internal disc disruption. In either case, greatest pain provoca- tion will be associated with movements and functions in the sagittal plane. Lumbar pain can also arise from afflictions within the zygapophyseal joint mechanism, as result of syno- vitis or chondropathy. Either of these conditions will produce the greatest pain provocation during three-dimensional move- ments, due to maximal stress to either the synovium or joint cartilage. Finally, patients can experience different symptoms associated with irritation to the dural sleeve, dorsal root gan- glion, or chemically irritated lumbar nerve root. Differential diagnosis of these conditions requires a thorough examina- tion and provides information that can assist the clinician in selecting appropriate management strategies.  Key Words: Lumbar, Disc, Zygapophyseal, Root INTRODUCTION The majority of all adults will complain of low back pain (LBP) at a given time in life with little or misleading evidence of pathology from imaging studies. 1–3 Holm suggested that mechanical, genetic, chemical, social, nu- tritional, and psychological factors can influence the on- set of LBP. 4 Investigators have deliberated over which structure or process is responsible for the low back symptoms and one can conclude that LBP can arise from a variety of different anatomical sites in concert with complex mechanical and neurophysiological processes that arise in response to trauma and disease. Conse- quently, a patient’s clinical presentation may initially be misleading to the diagnostician due to apparently simi- lar pain patterns that are produced by different afflic- tions. The observed similarities in different patients who present with complaints of LBP may be related to the in- tricacy of the sensory system that innervates the struc- tures in the lumbar region. 5 To insure effective diagnosis and focused management, the practitioner can imple- ment a clinical examination that attempts to reveal the structure or mechanism that is responsible for the pa- tient’s complaints. 6 Lumbar symptoms can be produced by pathological alterations in the intervertebral disc and zygapophyseal joints. 7,8 Additionally, afflictions at each of these sites appear to be inter-related. 9 Younger individuals with LBP are commonly afflicted with a primary disc-related disorder where the “soul” of their symptoms resides in acute mechanical and chemical changes in the disc. 10 However, the intervertebral disc demonstrates a symbi- otic relationship with the zygapophyseal joints (ZAJ) as these joints form a closed kinematic chain with the disc. 11,12 This relationship between disc and joints pro- motes segmental stability, and time-related disc pathol- ogy can produce degeneration and subsequent pain within the ZAJ. 13 This chain reaction suggests that sec- Address correspondence and reprint requests to: Phillip S. Sizer Jr, Med, PT, Texas Tech University Health Science Center, School of Allied Health, Physical Therapy Program, 3601 4th Street, Lubbock, TX 79430, U.S.A.