Low back pain is pain, muscle tension, or stiffness in the lower back with or without leg pain (sciatica). It is defined as chronic when it persists for 12 weeks or more. Non-specific low back pain is pain not attributed to a recognisable pathology (such as infection, tumour, osteoporosis, fracture or inflammation).
About 8 in 10 people suffer from low back pain at some stage of their life. In most cases it is a self-limiting condition and not due to any serious cause. In the vast majority the exact cause of back pain is unclear and labeled as non-specific low back pain. Sixty percent of patients with acute low back pain recover in six weeks and up to 80% to 90% recover with in 12 weeks.
Chronic back pain is relatively common. It can lead to significant disability and represents a major public health issue globally. It most cases the cause remains unknown. Back pain is best managed through a rehabilitative approach, with focus on core stability exercises. However injection treatments may be used to break the pain cycle and facilitate a rehabilitative approach in patients who fail to make progress with conservative management.
Some patients with low back pain continue to suffer on a long-term basis (greater than 3 months) and are labeled as having chronic low back pain. Chronic low back pain can be very disabling and have a detrimental effect on the individual in terms of functional as well as psychological wellbeing. Inappropriate medical advice can result in significant pain and disability.
Sciatica — Evidence of nerve root irritation typically manifests as sciatica, a sharp or burning pain radiating down the posterior or lateral aspect of the leg, usually to the foot or ankle. Pain radiating below the knee is more likely to represent true radiculopathy than proximal leg pain. Sciatic nerve pain is often associated with numbness or tingling. Sciatica due to disc herniation usually increases with coughing, sneezing, or performance of Valsalva maneuver.
Radiculopathy — Radiculopathy is a condition in which a disease process affects the function of one or more nerve roots. The clinical presentations of lumbosacral radiculopathy vary according the level of nerve root or roots involved. The most frequent are the L5 and S1 radiculopathies. Patients present with pain, sensory loss, weakness, and reflex changes consistent with the nerve root involved.
Cauda equina — Bowel or bladder dysfunction may be a symptom of severe compression of the cauda equina, which is a medical emergency. Urinary retention with overflow incontinence is typically present, often with associated saddle anesthesia, bilateral sciatica, and leg weakness. The cauda equina syndrome can be caused by a massive midline disc herniation or tumour.
Spinal stenosis — Nerve root entrapment in lumbar spinal stenosis is caused by narrowing of the spinal canal (congenital or acquired), nerve root canals, or intervertebral foramina. This narrowing is usually caused by bony hypertrophic changes in the facet joints and by thickening of the ligamentum flavum. Disc bulging and spondylolisthesis may contribute. Symptoms of significant lumbar spinal stenosis include back pain, transient tingling in the legs, and ambulation-induced pain localized to the calf and distal lower extremity, resolving with rest. This pain with walking, referred to as ‘pseudoclaudication’ or ‘neurogenic claudication’, is clinically distinguished from vascular claudication by the presence of normal arterial pulses.
The initial evaluation, including a history and physical examination, of patients with chronic low back pain should attempt to place patients into one of the following categories:
The medical history and examination should focus on red flags indicating the possibility of a serious underlying condition.
Psychosocial issues play an important role in guiding the treatment of patients with chronic low back pain. Patients with chronic low back pain who have a reduced sense of life control, disturbed mood, negative self-efficacy, high anxiety levels, and mental health disorders, and who engage in catastrophizing tend to respond less well to treatments. ‘Yellow flags’ are psychosocial risk factors for long-term disability. Evaluation of psychosocial problems and yellow flags are useful in identifying patients with a poor prognosis.
Yellow flags include:
The basic physical examination should include the following components:
Inspection of back and posture – Inspection of the patient on physical examination can reveal anatomic abnormalities such as scoliosis (lateral spinal curvature) or kyphosis (spinal curvature with posterior convexity).
Range of motion in flexion and extension does not reliably distinguish among pathologic causes, but can provide a baseline to use as an index of therapeutic response. Limited lumbar flexion is not sensitive or specific for diagnosing ankylosing spondylitis.
Palpation of the back is usually performed to assess vertebral or soft tissue tenderness. Vertebral tenderness is a sensitive, but not specific, finding for spinal infection. However, the finding of soft tissue tenderness is poorly reproducible among observers.
The straight leg raise test may be useful to help confirm radiculopathy. Straight leg raising is done with the patient supine. The test is considered positive when the sciatica is reproduced between 10 and 60 degrees of elevation.
The crossed straight leg raising test refers to elevation of the unaffected leg. The test is positive when lifting the unaffected leg reproduces the sciatica in the affected leg. The seated straight leg test is done while the patient is in the seated position and the lower leg is slowly extended until the leg is flexed at the hip to 90 degrees. If sciatica is present, the pain will be reproduced as the leg is extended.
A positive straight leg test has limited sensitivity and specificity for herniated disc (64 and 57% respectively). The crossed straight leg test is less sensitive for herniated disks, but has 90% specificity.
Neurologic assessment of L5 and S1 roots – For patients suspected of having a disc herniation, neurologic testing should focus on the L5 and S1 nerve roots, since 98 percent of clinically important disc herniations occur at L4-5 and L5-S1. Absent reflexes can occur in 30 percent of those between ages 61 and 70 and nearly 50 percent of those aged 81 to 90.
Peripheral pulses – Especially in older patients with exercise-induced calf pain to rule out vascular claudication.
Nonorganic signs or Waddell’s signs – In patients with chronic pain, psychological distress may amplify low back symptoms, and may be associated with anatomically ‘inappropriate’ physical signs. The most reproducible of these signs are superficial tenderness, distracted straight leg raising (ie, discrepancy between seated and supine straight leg raising tests), and the observation of patient overreaction during the physical examination, also known as Waddell’s signs. Other Waddell’s signs suggestive of symptom enhancement include non dermatomal distribution of sensory loss, sudden giving way or jerky movements with motor examination, inconsistency in observed spontaneous activity (dressing, getting off table) and formal motor testing, and pain elicited by axial loading. The presence of multiple Waddell’s signs may suggest a behavioral component to a patient’s pain. However, systematic reviews have not found an association between Waddell’s signs and psychological distress, or claims for disability compensation or litigation.
Imaging has limited utility because most patients with chronic low back pain have nonspecific findings on imaging and asymptomatic patients often have abnormal findings. MRI, which is the preferred imaging modality is only recommended for patients with red flags for serious or rapidly progressive disease or radicular symptoms that do not spontaneously resolve after six weeks.