Important Clinical Distinctions Spinal Stenosis and Disc painSpinal stenosis usually presents with pain radiating beyond the back to the buttocks, thighs or lower legs. The pain is worsened with extension of the lumbar spine (eg, standing or walking) and improves with flexion of the spine (eg, sitting or stooping forward). This is in contrast to pain originating from a disc which is typically worsened by lumbar flexion Myofascial painThe features of myofascial low back pain include diffuse low back pain of gradual onset which worsens after resting or sitting. The pain is aggravated by cold and relieved by warmth and movement. There is often associated stiffness and limited range of motion, with a sensation of tightness in the back. Bilateral leg pain and paresthesia may occur, but limping and listing are unusual. Tenderness is present within the affected muscle and soft tissues, and often the sacroiliac joints. Fibromyalgia may also present as back pain with these features. Severe, constant back pain, persisting at night, suggests the presence of neoplasm, infection, or lateral recess nerve root compression. Thoracolumbar fractures present with back pain and segmental radiation in the distribution of the contiguous nerve roots. Sitting often aggravates the pain and muscle spasm may disturb sleep. Dorsal kyphosis, "dowager hump", and loss of height may be noted. Compression fracture may be the first symptom of osteoporosis. Sciatica Sciatica, which refers to pain radiating in a dermatomal distribution is highly suggestive of a herniated disc. The classic features are aching pain in the buttock and paresthesias radiating into the posterior thigh and calf or into the posterior lateral thigh and lateral foreleg. In most nerve root syndromes, a precise description of radiating pain will help localize to a nerve root level. Over 95 percent of herniated discs affect the L4-5 or L5-S1 interspace. The sensitivity of sciatica (the proportion of patients with a herniated disc who have sciatica) was 0.95 in one report, indicating that its absence makes lumbar disc herniation unlikely. The specificity of sciatica (the percentage of patients without a herniated disc who do not have sciatica) is also high at approximately 0.88. However the diagnosis should not be based solely on the presence or absence of sciatica. Irritation of non-neural structures in the lumbar spine, such as the facet joints and numerous ligaments and other supporting structures, can produce radiating pain in the lower extremities which can cause diagnostic confusion in some patients. Furthermore, radicular pain ("sciatica") can be caused by such diverse entities as neoplasms, spinal stenosis, entrapment neuropathy, myofascial pain syndromes, trochanteric bursitis, vascular malformations, endometriosis, diabetic radiculoneuropathy, herpes zoster (shingles), idiopathic lumbosacral plexitis, and entrapment of the sciatic nerve by the pyriformis muscle. Table 3: Differences between the pain of a herniated disc and spinal stenosis Characteristic Spinal stenosis Disc-pain Aggravating factor Lumbar extension Lumbar flexion (standing, sitting) Relieving factor Lumbar flexion (sitting Lumbar extension (lying or stooping over) down) Table- 4 Nerve Root Pain worst in Radiation Sensory Motor Reflexes of pain loss weakness S1 Leg>>Back Buttock, Fifth toe flexors, Absent ankle posterior lateral foot gastrocne- thigh, mius PL calf and PL calf and rarely jerk heel PL thigh hamstrings L5 Back >>Leg PL thigh, great toe externsor no reflex groin, medial foot hallucis loss lateral Calf and DM AL calf longus, foot, first (less often) Tibialis anterior Two toes and peronii- foot drop L4 or L3 Back >> Leg AM thigh AM thigh Quadriceps Absent knee and jerk iliopsoas.