Low back pain (LBP) is the most common pain condition seen in pain clinics. Approximately 60% to 80% of the Unites States population will experience back pain at some point time during life. It is critical for clinicians to appropriately examine the patients and make a diagnosis before treatment is rendered.
Common Causes of Low Back Pain
Common causes of LBP include muscle strain, lumbar disc herniation, lumbar radiculopathy (sciatica), lumbar facet joint syndrome, sacroiliac joint syndrome and lumbar spinal stenosis.
Patients with acute muscle strain in the low back often have histories of acute injury. Physical examination may reveal tenderness or muscle spasms. Non-steroidal anti-inflammatory drugs (NSAIDs), muscle relaxants, massage therapy, physical therapy or acupuncture often provide effective pain relief. However, many times muscle pain in the low back is secondary to injuries in deeper tissues such as lumbar disc herniation or lumbar radiculopathy.
Acute lumbar disc herniation after injury may cause severe low back pain. Patients often complain of severe, shooting, or stabbing pains in the low back with frequent radiating pain down the dorsomedial part of the foot when the L5 nerve root is involved, or the lateral part of the foot or the small toe when the S1 nerve root is involved. Straight leg raising test is often positive. Detail neurological examinations may find decreased sensation to pin prick in the area innervated by L5 and/or S1 nerve root(s). Patient may also have mild weakness on the tibialis anterior (L5), or peroneous longus and brevis muscles (S1). These patients usually have severe tenderness and spasm over the lumbar paraspinal muscles.
Lumbosacral MRIs may find disc herniation at L4-5 and/or L5-S1 level(s). EMG/NCV tests may not detect a lumbar radiculopathy. NSAIDs, muscle relaxants, and physical therapy may help some of patients with acute disc herniation and lumbar radiculopathy. If patients fail these treatments, lumbar epidural corticosteroid injections may offer fast and effective pain relief if the nerve roots are not severely mechanically compressed. Open surgeries are suggested for those with severe focal weakness of relevant muscles or incontinence. Surgery may also be indicated for severe pain that lasts for more than 3 months and does not respond to aggressive pain management if disc herniation is demonstrated by MRI or CT studies.
Lumbar facet joint syndromes are found in up to 35% of patients with LBP. It is frequently associated with arthritis or injuries in lumbar facet joints. Patients may complain of pain in the low back, often on one side only. Pain may radiate down the back or front of the thigh. Physical examination may find positive tenderness over the lumbar paraspinal muscles and facet joints. Back extension and lateral rotation to the side of the pain often increases the back pain. Results of a straight leg raising test should be negative. Neurological examination should be normal unless there is a coexistent lumbar radiculopathy or other neurological condition.
Diagnosis of facet joint syndrome is clinical. MRI and CT reports of facet joint arthropathy are not well correlated with clinical findings. Often, these changes are age-related. NSAIDs should be tried for those with lumbar facet joint syndromes before the patients are considered for diagnostic medial branch block or intra-joint corticosteroid injections.
Sacroiliac (SI) joint syndrome is another major source of low back pain. The patient may have pain in one side of the low back with pain radiation down to the hip or thigh. Pain is often increased when the patients try to walk upstairs. Physical examination may find tenderness over the SI joint. Patrick’s test or single leg standing test often exacerbates the SI joint pain. NSAIDs are the first line mediation for SI joint inflammation. SI joint corticosteroid injection can provide temporary pain relief. Radiofrequency lesions to denervate the SI joint have been reported to be effective, however, more studies are needed to confirm this.
Lumbar spinal stenosis is a common age-related change. The majority of senior citizens over 60 years old have varying degrees of spinal stenosis due to disc herniation, disc bulging, osteophytes or degenerative spondylolisthesis. Pre-existing congenital lumbar canal stenosis predisposes to the development of this syndrome.
Fortunately, less than 30% of those with spinal stenosis have clinical pain. Patients often have pain in the low back with pain radiation down the back of both legs. Standing or walking may make the pain worsen. Patients often walk with a hunched back and sit down after walking a short distance to relieve pain (neurogenic claudication). The pain usually takes minutes to disappear, compared to the seconds with vascular claudication. On physical examination, patients often have no tenderness over the lumbar spine. A straight leg raising test may be normal. The condition must be separated from vascular claudication.
Patients may try NSAIDs first. Lumbar corticosteroid injections may provide pain relief for this group of patient for weeks or to months. If a patient has severe pain and does not wants surgery, chronic narcotic treatment often provides adequate pain control, but runs a risk of the development of tolerance and addiction.