Approach
Musculoskeletal lower back pain can be diagnosed clinically from the history and physical exam. It is an exclusion diagnosis; therefore, the clinician must eliminate specific lower back pain causes of neurologic compromise, neoplasia, inflammatory arthritis, fracture, or referred pain from other locations or organ systems.
History
Patients with lower back pain should be questioned regarding prior lower back pain episodes and treatments, onset, duration, location, radiation, character, aggravating and relieving factors, and severity. Musculoskeletal lower back pain may be dull, gnawing, tearing, burning, electric, and/or associated with muscle spasms. History of previous therapies should be obtained, including physical therapy, acupuncture, massage, transcutaneous electrical nerve stimulation, medications, injections, spinal manipulation, or surgery.
History should include a specific enquiry about radicular symptoms of leg pain, paresthesia, numbness, and weakness. Typically, musculoskeletal lower back pain does not radiate to the legs. If it does, the pain does not travel below the knee. If pain is located below the knee, it cannot solely be attributed to musculoskeletal lower back pain, and the differential broadens to include pathology such as radiculopathy, spinal stenosis, peripheral neuropathy, vascular claudication, and pathology of the lower extremities.[3]
History should also be directed toward excluding red flags:[3][4]
Recent significant trauma, or milder trauma in age >50 years
Unexplained weight loss
Immunosuppression
History of cancer
Intravenous drug use
Urinary tract infection
Prolonged use of corticosteroids
Osteoporosis
Focal neurologic deficit with progressive or disabling symptoms
Acute onset of urinary retention or overflow incontinence
Fecal incontinence or loss of anal sphincter tone
Saddle anesthesia
Global or progressive lower limb motor weakness
Duration of lower back pain >6 weeks, not improving with conservative management.
If a red flag is present, further investigation and imaging are needed. The presence of a red flag indicates lower back pain potentially associated with another specific cause, including cauda equina syndrome, neoplasia, infection, vertebral fracture, inflammatory arthritis, and referral from another organ system (i.e., pyelonephritis) or location (i.e., sacroiliac dysfunction). Spinal infection is common in people with conditions associated with immunosuppression, symptoms of spinal infection may include fever and neurologic dysfunction.[61]
Once a diagnosis of nonspecific lower back pain is established, further inquiry into functional, occupational, social, and psychiatric history should be sought to address risk factors, including obesity, occupational risks, smoking, and psychosocial stressors. Psychiatric comorbidities such as depression, anxiety, and somatization increase the risk of progression to chronic disabling pain.[62] Risk factors for worst outcomes at 1 year include maladaptive pain-coping behavior, nonorganic signs, functional impairment, poor general health, and the presence of psychiatric comorbidities.[34]
Available evidence suggests that the clinician should consider consulting psychiatry if mood or anxiety disorders are suspected.[34][35]
Physical exam
A focused musculoskeletal and neurologic exam should be performed.
Focused musculoskeletal exam
The spine should be inspected for obvious deformity (e.g., in fractures) and abnormal curvature (scoliosis, kyphosis, lordosis) that can create pain in a minority of cases. This should prompt the clinician to order x-rays to document baseline curvature and orthopedic referral for moderate to severe cases.
The spinous processes and musculature should be palpated, feeling for taut bands, which create pain only in the location touched, and trigger points (may feel knot-like) that produce referred pain elsewhere. These findings suggest myofascial pain.
Assess the active and passive range of motion (ROM) by asking the patient to stand and actively flex, extend, and laterally flex as far as they can. Pain on flexion that radiates to the leg suggests disk herniation with impingement on a nerve root; pain on extension can suggest either facet arthropathy or spinal stenosis. Greatly restricted ROM in a younger patient may suggest ankylosing spondylitis.
Every patient with lower back pain should have a hip exam. Passive ROM of each hip should be assessed with the patient lying supine. There should be normally 135° of flexion, extension to 15° beyond neutral, and approximately 45° of internal and external rotation. Pain in any of these motions suggests hip pathology and hip x-rays should be obtained.
Additional tests may be performed, depending on the differential diagnoses under consideration.
Schober test
Performed when ankylosing spondyloarthritis is suspected. The midpoint of the posterior superior iliac spine is located and a point 10 cm above and another point 5 cm below is marked with a pen. The patient is asked to flex forward maximally, and the distance between the 2 marked points is measured. A positive test is when the distance between these 2 marks is <20 cm. A positive Schober test in combination with positive findings on sacroiliac (SI) exam, age <40 years, or positive family history should prompt referral to a rheumatologist.
FABER (flexion, abduction, and external rotation of the hip) test
Assesses for both hip and SI pathology depending on whether pain is felt in the hip or SI joint. It is performed by asking the patient to lie supine, and then by flexion, abduction, and external rotation of their hip joints.
Gaenslen test
Assesses for SI joint pathology. It is performed by having patients lie supine at the edge of the exam table, and asking them to flex one hip ("bring knee to chest") while extending the other hip over the edge of the exam table ("hang your leg over the table"). Pain in either SI joint suggests pathology. If such tests are positive, lumbosacral x-rays should be obtained. If there is SI pathology in combination with restricted spine flexion/extension, referral to a rheumatologist is warranted.
Straight leg raise test
Assesses for radiculopathy. With the patient supine, 1 leg is lifted upward by flexing the hip while keeping the knee extended. If the patient experiences pain radiating beyond the knee with this maneuver, the test is positive and suggests a radiculopathy. Note: this test is not positive if the patient experiences discomfort in the back or hamstring area (commonly due to muscle stretch created by this maneuver).
Focused neurologic exam
Assesses motor strength, sensation to temperature and light touch, and deep-tendon reflexes (DTRs).
Motor exam should include manual muscle testing of hip flexion, hip extension, knee flexion, knee extension, ankle plantar flexion, ankle dorsiflexion, and great toe extension and flexion.
Sensory exam: perception of light touch, pin prick, and vibration sense in the buttock, perianal region, and lower extremities is tested. This should be equal bilaterally.
Reflexes in the patellar (L4) and ankle (S1) are tested.
Plantar response test: the bottoms of both feet are scratched with a sharp object along the lateral plantar surface of the foot and then crossing over to the medial surface around the region of the first metatarsophalangeal joint. An upgoing great toe with other toes fanning out is a positive response and suggests upper motor neuron pathology; a downgoing great toe is normal.
Diagnostic considerations should be reassessed if abnormalities are found on neurologic exam. The focus should be on further classifying the pattern as follows.
Myelopathy/radiculopathy
Suggested by a combination of sensory loss below a level, upper motor neuron signs (such as increased reflexes or upgoing plantar response), and motor weakness below a level.
Special attention should be paid to the perianal area, and in particular to decreased rectal tone, which can suggest a cauda equina lesion and requires immediate investigation.
Myelopathies are due to problems with the spinal cord and can be secondary to spinal stenosis, in addition to less common etiologies such as demyelinating disease, syphilis, vascular insufficiency, transverse myelitis, or vitamin B12 deficiency.
Radiculopathy is suggested by dermatomal and myotomal deficits. If either myelopathy or radiculopathy is suggested on exam, a lumbosacral magnetic resonance imaging (MRI) should be obtained, and referral to a spine specialist considered if neurologic symptoms are severe or progressive.
Peripheral neuropathy/plexopathy
Suggested by lower motor neuron signs of weakness and decreased DTRs; the most common causes of these symptoms are diabetic peripheral neuropathy and diabetic amyotrophy.
If peripheral neuropathy or plexopathy is suggested by the pattern of motor, sensory, or reflex impairment, further investigation with electromyogram is indicated. Do not order an electromyogram for low back pain unless there is leg pain (sciatica), weakness or numbness.[63][64]
Laboratory and imaging studies
Evaluation of the lower back pain patient with laboratory/imaging studies should only be done based on clinical suspicion of certain scenarios or when pain is ongoing for >6 weeks despite conservative management.[3][63][65][66][67][68][69][70]
MRI without intravenous contrast is the preferred first-line investigation for the majority of patients with symptom duration greater than 6 weeks.[3]
Imaging studies and/or additional investigations are needed for patients presenting with red flags: recent significant trauma; unexplained weight loss; immunosuppression; history of cancer; intravenous drug use; urinary tract infection; prolonged use of corticosteroids; minor fall or heavy lift in a potentially osteoporotic or elderly person; focal neurologic deficit with progressive or disabling symptoms; acute onset of urinary retention or overflow incontinence; loss of anal sphincter tone or fecal incontinence; saddle anesthesia; global or progressive motor weakness in the lower limbs; or duration of lower back pain >6 weeks.[3][4][65][68][69][66][70]
If a fracture is suspected, the initial investigation should be an x-ray of the lumbar spine. If there is persistent concern for a vertebral body fracture, computed tomography (CT) scan is performed for detailed bone analysis.[3] If a neoplasm or infection is suspected, MRI lumbar spine with and without intravenous contrast is the investigation of choice.[3]
Suspected cauda equina syndrome
MRI without intravenous contrast is the imaging study of choice for the evaluation of patients with suspected cauda equina syndrome.[3]
Cauda equina syndrome is a neurosurgical emergency that requires immediate referral for further management. See Cauda equina syndrome (Management approach).
Progressive pain or sensory or motor disturbances in lower extremities
Suggests neurologic symptoms. This warrants a lumbosacral MRI to assess the degree of neurologic impingement on the nerve roots or spinal cord. If MRI is contraindicated, CT myelogram is an appropriate substitute.
Suspicion of ankylosing spondylitis or other rheumatologic disorders
A history of morning stiffness lasting >1 hour, positive family history, or symmetric joint pains should prompt referral to a rheumatologist. Before this referral, basic labs such as complete blood count (CBC), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) as well as spinal x-ray (including SI joints) can be ordered to help serve as an initial starting point for rheumatologic workup.
Osteomyelitis
History of intravenous drug use, tuberculosis risk factors, immunosuppression, or presence of fevers/chills should prompt consideration of osteomyelitis. Fever, fluctuance and exquisite spinal tenderness on exam may be present. CBC, ESR, CRP, and blood cultures should be ordered. If tuberculosis is suspected, a purified protein derivative (PPD) should be placed. In all cases, imaging workup should begin with a lumbosacral spine x-ray.
If there is no evidence of osteomyelitis, but this is still suspected, a bone scan should be ordered. Again if there is no evidence of osteomyelitis, but clinical suspicion is still high, then a lumbosacral MRI, which has high sensitivity, should be ordered.
Some clinicians bypass the bone scan and proceed to MRI if plain films are negative. If any of the imaging studies are positive, an orthopedic referral should be considered.
Suspicion regarding malignancy
May arise if a patient has a history of cancer, unexplained weight loss, unrelenting night pain, or rest pain. An age- and sex-appropriate cancer screening should be initiated.
Pyelonephritis
Can result in low back or flank pain. Patients usually report other symptoms including malaise, fevers, chills, and dysuria. Urinalysis and culture may assist diagnosis.
Use of this content is subject to our disclaimer