ESSENTIALS OF DIAGNOSIS
The cause of back pain may be categorized by pain on flexion versus pain on extension.
Nerve root impingement is suspected when pain is leg-dominant rather than back-dominant.
Alarming signs for serious spinal disease include unexplained weight loss, failure to improve with treatment, severe pain for more than 6 weeks, and night or rest pain.
The cauda equina syndrome often presents with bowel or bladder symptoms (or both) and is an emergency.
Low back pain is the most common cause of disability for patients under the age of 45 and is the second most common cause for primary care visits. The annual prevalence of low back pain is 15–45%, and the annual cost in the United States is over $50 billion. Approximately 80% of episodes of low back pain resolve within 2 weeks and 90% resolve within 6 weeks. The exact cause of the low back pain is often difficult to diagnose; its cause is often multifactorial, although there are usually degenerative changes in the lumbar spine.
Alarming symptoms for back pain caused by cancer include unexplained weight loss, failure to improve with treatment, pain for more than 6 weeks, and pain at night or rest. History of cancer and age > 50 years are other risk factors for malignancy. Alarming symptoms for infection include fever, rest pain, recent infection (urinary tract infection, cellulitis, pneumonia), or history of immunocompromise or injection drug use. The cauda equina syndrome is suggested by urinary retention or incontinence, saddle anesthesia, decreased anal sphincter tone or fecal incontinence, bilateral lower extremity weakness, and progressive neurologic deficits. Risk factors for back pain due to vertebral fracture include use of corticosteroids, age > 70 years, history of osteoporosis, recent significant trauma, or very severe focal pain. Back pain may also be the presenting symptom in other serious medical problems, including abdominal aortic aneurysm, peptic ulcer disease, kidney stones, or pancreatitis.
The physical examination is best done with the patient in the standing, sitting, supine, and then prone positions to avoid frequent repositioning of the patient. In the standing position, the patient's posture can be observed. Commonly encountered spinal asymmetries include scoliosis, thoracic kyphosis, and lumbar hyperlordosis. The active range of motion of the lumbar spine can be assessed. The common directions include flexion, rotation, and extension. The one-leg standing extension test assesses for pain as the patient stands on one leg while extending the spine. A positive test can be caused by pars interarticularis fractures (spondylolysis ...