Back pain with lower extremity pain – how often is it related to the nerve root?

Degenerative disorders that affect nerve roots – lumbar disc herniation and lumbar spinal stenosis - account for the majority of back-related lower limb pain, probably over 80%^1,2, but what conditions account for the remainder?

One study showed that pain drawings of people with back and lower extremity pain often does not correlate well with magnetic resonance imaging for nerve root compression in the lumbar spine, except for when pain reaches the foot.³ Another study found that pain distal to the knee has an odds ratio of 2.62 for nerve root compression in patients with back pain⁴. The further distal in the leg the patient feels symptoms, the more likely a nerve root is involved. However, there are still many conditions that cause back pain and pain distal to the knee that do not affect the nerve roots. 

Data from Rankine et al, diagram by Robert Trager

Sacroiliac joint pain can refer distal to the knee in 28% of cases, and into the foot in 14%⁵. Chronic zygapophyseal joint-mediated low back pain may refer distal to the knee in up to 40% of cases⁶. Peripheral nerve entrapments can also cause back pain and leg pain. A major study identified that in 4,000 patients with symptoms of lumbosacral radiculopathy (including back and leg pain), 36 patients (0.9%) were found to have a peripheral nerve entrapment as the cause of their symptoms⁷. In another study of 3,550 patients with sciatica, piriformis syndrome was diagnosed in 26 cases (0.7%)⁸.

A group of related myofascial disorders has become notorious for mimicking nerve root problems of the low back: Greater trochanteric pain syndrome, trochanteric bursitis, and iliotibial band syndrome. Of 247 patients referred to a spinal surgery center for low back pain, 51 patients (20.2%) were found to have greater trochanteric pain syndrome⁹. In another study of 170 patients with suspected radiculopathy, trochanteric bursitis or iliotibial band syndrome were found in 29% of patients¹⁰.

Rarely, the lumbosacral plexus is affected by a mass lesion such as a pelvic tumor or hematoma which can lead to back and leg pain. Possibly the most overlooked of these is catamenial sciatica, a condition whereby endometriosis affects the sciatic or other nerves of the lower extremity and causes sciatica that coincides with menstruation^11,12.

There are even much rarer causes of back and leg pain mediated through spinal cord lesions. These include the rare thoracic disc herniation^13,14 and multiple sclerosis¹⁵.

Leg image taken from Gray's anatomy, text by Robert Trager

Despite the fact that a majority of cases of back-related leg pain are caused by disc herniation and spinal stenosis, the other joints (sacroiliac, zygapophyseal), myofascial structures, peripheral nerves and spinal cord cannot be overlooked based on these symptoms alone.

1.       Hasankhani, E. G. & Omidi-Kashani, F. Magnetic Resonance Imaging versus Electrophysiologic Tests in Clinical Diagnosis of Lower Extremity Radicular Pain. ISRN Neurosci. 2013, 1–4 (2013).

2.       Schmutzhard, E., Mohsenipour, I. & Stanek, G. Incidence of nervous system Borrelia burgdorferi infection in patients with lumboradicular syndrome. Eur. Neurol. 33, 149–151 (2008).

3.       Rankine, J. J., Fortune, D. G., Hutchinson, C. E., Hughes, D. G. & Main, C. J. Pain drawings in the assessment of nerve root compression: a comparative study with lumbar spine magnetic resonance imaging. Spine 23, 1668–1676 (1998).

4.       Beattie, P. F., Meyers, S. P., Stratford, P., Millard, R. W. & Hollenberg, G. M. Associations between patient report of symptoms and anatomic impairment visible on lumbar magnetic resonance imaging. Spine 25, 819–828 (2000).

5.       Slipman, C. W. et al. Sacroiliac joint pain referral zones. Arch. Phys. Med. Rehabil. 81, 334–338 (2000).

6.       Manchikanti, L., Pampati, V., Fellows, B. & Baha, A. G. The inability of the clinical picture to characterize pain from facet joints. Pain Physician 3, 158–166 (2000).

7.       Saal, J. A., Dillingham, M. F., Gamburd, R. S. & Fanton, G. S. The pseudoradicular syndrome. Lower extremity peripheral nerve entrapment masquerading as lumbar radiculopathy. Spine 13, 926–930 (1988).

8.       Jawish, R. M., Assoum, H. A., Khamis, C. F. & others. Anatomical, clinical and electrical observations in piriformis syndrome. J Orthop Surg Res 5, 3 (2010).

9.       Tortolani, P. J., Carbone, J. J. & Quartararo, L. G. Greater trochanteric pain syndrome in patients referred to orthopedic spine specialists. Spine J. 2, 251–254 (2002).

10.     Cannon, D. E., Dillingham, T. R., Miao, H., Andary, M. T. & Pezzin, L. E. Musculoskeletal Disorders in Referrals for Suspected Lumbosacral Radiculopathy. Am. J. Phys. Med. Rehabil. 86, 957–961 (2007).

11.     Yekeler, E. et al. Cyclic sciatica caused by infiltrative endometriosis: MRI findings. Skeletal Radiol. 33, 165–168 (2004).

12.     Missmer, S. A. & Bove, G. M. A pilot study of the prevalence of leg pain among women with endometriosis. J. Bodyw. Mov. Ther. 15, 304–308 (2011).

13.     Cho, H.-L., Lee, S.-H. & Kim, J.-S. Thoracic Disk Herniation Manifesting as Sciatica-Like Pain. Neurol. Med. Chir. (Tokyo) 51, 67–71 (2011).

14.     Lyu, R.-K., Chang, H.-S., Tang, L.-M. & Chen, S.-T. Thoracic disc herniation mimicking acute lumbar disc disease. Spine 24, 416–418 (1999).

15.     Marchettini, P., Formaglio, F. & Lacerenza, M. Pain as heralding symptom in multiple sclerosis. Neurol. Sci. 27, s294–s296 (2006).