A 60-year-old woman presents to the emergency department with back pain after gardening. Her pain is 7/10 in severity, non-radiating, and not relieved by rest. She has never experienced this pain in the past and denies fever, night sweats, unintentional weight loss, and bowel or bladder incontinence. She has hypertension for which she takes hydrochlorothiazide and had a recent asthma flare requiring a prednisone taper. She does not drink alcohol or smoke. Her temperature is 98.6°F (37.0°C), blood pressure is 120/80 mmHg, pulse is 90/min, and respirations are 18/min. Physical exam reveals an uncomfortable middle-aged woman in no acute distress. There is no tenderness to palpation of the spinous processes. Flexion of the hip with the knee extended while the patient is supine does not elicit any pain, nor does forced dorsiflexion of the foot at terminal hip extension. She has 5/5 strength to hip flexion, extension, abduction, and adduction; knee flexion and extension; and ankle dorsiflexion and plantarflexion bilaterally. Bilateral patellar and Achilles reflexes are 2+. Serum laboratory results are as follows: Hemoglobin: 12.0 g/dL Creatinine: 1.1 mg/dL Ca2+: 10.6 mg/dL Which of the following is the most likely diagnosis?
Spondylolisthesis
Lumbosacral strain
Herniated disc
Multiple myeloma
Lumbosacral strain
This patient presents with acute low back pain after physical exertion without radicular signs (e.g., motor or sensory changes in a nerve root distribution) and a negative straight leg raise, which are most consistent with lumbosacral strain.

The evaluation of acute low back pain is focused on eliciting clinical history and signs that would indicate further work-up. In patients without significant trauma, the presence of signs of spinal cord compression (e.g., urinary retention, bowel incontinence, saddle anesthesia, focal neurologic deficits), history of or strong risk factors for cancer, signs of infection, or risk of vertebral compression fracture should prompt additional work-up with imaging such as radiographs or magnetic resonance imaging. If none of these findings are present (most patients with acute low back pain in the primary care setting), then conservative therapy for 4-6 weeks consisting of non-steroidal anti-inflammatory drugs with or without physical therapy is indicated.

Patel and Ogle review the management of acute low back pain in the primary care setting. They outline the Waddell signs, which indicate the presence of a functional (signs of excessive pain behavior) aspect of pain. The authors recommend surgical evaluation only in patients with worsening neurologic deficits or intractable pain resistant to conservative treatment.

Incorrect Answers:
Answer A: Herniated discs occurs when the nucleus pulposus herniates through a weakened part of the annulus fibrosus of an intervertebral disc, resulting in spinal nerve root compression. This causes radicular findings at the level of compression, including weakness in hip abduction and ankle dorsiflexion with L5 involvement and weakness in ankle plantarflexion and reduced Achilles reflex with S1 involvement, and radiation of pain into the ipsilateral lower extremity. The straight leg raise test would be positive, as it exacerbates the nerve root compression.

Answer C: Multiple myeloma presents with hypercalcemia, anemia, renal failure, and lytic bone lesions causing bone pain. This patient has no constitutional symptoms to suggest a malignant process and has a mild elevation in serum calcium, which is likely due to her thiazide diuretic. The clear association of her back pain with exertion makes lumbosacral strain more likely.

Answer D: Spondylolisthesis occurs when a vertebral body is forwardly subluxated relative to the adjacent vertebral body. This presents as back pain alleviated by rest. Since this can narrow the spinal canal, it may also present with neurogenic claudication, manifesting as buttock or leg pain with walking that can be alleviated by bending forward. This patient’s back pain is not alleviated by rest and is associated with exertion.

Answer E: Vertebral compression fractures can present as back pain in a patient with minor or no trauma. These patients have osteoporosis and other risk factors like advanced age or chronic corticosteroid use and would have point tenderness at the site of fracture. This patient does not have point tenderness or risk factors.

Bullet Summary:
Lumbosacral strain is a common cause of acute low back pain that presents after physical exertion with no radicular signs and a negative straight leg raise test.