Musculoskeletal · Low Back Pain
The facts most likely to be tested
Lumbar strain is a diagnosis of exclusion characterized by paraspinal muscle tenderness and lack of radicular symptoms.
The straight leg raise test is typically negative in patients with simple lumbar strain, helping to rule out lumbar disc herniation.
Red flags requiring immediate imaging include fever, unexplained weight loss, history of malignancy, or progressive neurologic deficits.
Cauda equina syndrome is a surgical emergency presenting with saddle anesthesia, bowel or bladder incontinence, and bilateral lower extremity weakness.
First-line management for acute lumbar strain consists of patient education, continuation of normal activity as tolerated, and NSAIDs.
Bed rest is discouraged for acute low back pain as it delays recovery and increases the risk of deconditioning.
Imaging is not indicated for patients with non-specific low back pain in the absence of red flags during the first 6 weeks of symptoms.
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A 34-year-old male presents to the clinic complaining of acute lower back pain after lifting a heavy box yesterday. He describes the pain as a dull ache localized to the paraspinal muscles without radiation to the legs. Physical examination reveals tenderness to palpation over the lumbar muscles and full range of motion limited only by pain. The straight leg raise test is negative bilaterally, and neurologic examination is intact with normal strength, sensation, and reflexes. He has no history of trauma, fever, or weight loss.
What is the most appropriate next step in management?
NSAIDs and encouragement to remain active as tolerated
The patient presents with classic signs of a lumbar strain without red flags, making conservative management the standard of care as per the 'first-line management' and 'imaging' bets.
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High yield triage
Etiology / Epidemiology
Most common cause of low back pain; typically follows heavy lifting or sudden twisting.
Clinical Manifestations
Paraspinal muscle tenderness and lack of radiculopathy; no neurological deficits.
Diagnosis
A clinical diagnosis of exclusion; imaging is not indicated for uncomplicated cases.
Treatment
First-line is NSAIDs and activity modification; avoid prolonged bed rest.
Prognosis
Self-limiting; 90% of patients recover within 4 weeks.
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Epidemiology & Etiology
Affects all ages, peaking in the 30-50 year range. Primary risk factors include obesity, sedentary lifestyle, and improper lifting mechanics. It is the most frequent cause of primary care visits for musculoskeletal pain.
Pertinent Anatomy
Involves the erector spinae muscle group and associated ligaments. The lumbar spine lacks the stability of the thoracic cage, making it vulnerable to mechanical stress.
Pathophysiology
Micro-tearing of muscle fibers or ligaments leads to an inflammatory cascade. This results in muscle spasms and localized pain. The process is typically self-limiting as tissue repair occurs.
Clinical Manifestations
Patients present with localized, non-radiating pain exacerbated by movement. Paraspinal muscle tenderness is the hallmark finding. Red flags requiring immediate imaging include fecal/urinary incontinence, saddle anesthesia, or progressive motor weakness.
Diagnosis
Diagnosis is clinical. Imaging is reserved for patients with red flags or pain persisting >6 weeks. MRI is the gold standard if structural pathology or malignancy is suspected.
Treatment
Initial management focuses on NSAIDs for pain control and maintaining activity. Avoid prolonged bed rest as it delays recovery. Muscle relaxants may be used short-term, but physical therapy is the preferred long-term strategy.
Prognosis
Excellent; 90% of patients return to baseline function within one month. Chronic pain develops in <5% of cases. Monitor for the development of radiculopathy or neurological decline.
Differential Diagnosis
Herniated disc: positive straight leg raise
Vertebral compression fracture: history of osteoporosis or trauma
Spinal stenosis: shopping cart sign (relief with flexion)
Cauda equina syndrome: urinary retention
Malignancy: night pain and unexplained weight loss