Episode 194: Acute low back pain.  

Future Dr. Ibrahim presents a clinical case to explain the essential points in the evaluation of back pain.  Future Dr. Redden adds information about differentiating between a back strain and more serious diseases such as cancer, and Dr. Arreaza shares information about returning to work after back strain.

Written by Michael Ibrahim, MSIV. Editing and comments by Jordan Redden, MSIV, and Hector Arreaza, MD.

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Dr. Arreaza:
Welcome back, everyone. Today’s topic is one that every primary care provider, emergency doctor, and even specialist sees routinely: low back pain. It's so common that studies estimate up to 80% of adults will experience it at some point in their lives. But despite how frequent it is, the challenge is to identify which cases are benign and which demand urgent attention.

Jordan:
Exactly. Low back pain is usually self-limiting and mechanical in nature, but we always need to keep an eye out for the rare but serious causes: things like infection, malignancy, or neurological compromise. That’s why a good history and physical exam are our best tools right out of the gate.

Michael:
And to ground this in a real example, let me introduce a patient we saw recently. John is a 45-year-old warehouse worker who came in with two weeks of lower back pain that started after lifting a 50-lb box. He describes it as a dull, aching pain that radiates from his lower back down the posterior left thigh into the calf. He says it gets worse with bending or coughing, but he feels better when lying flat. He also mentioned some numbness in his left foot, but he denies any bowel or bladder issues. His vitals are completely normal. On exam, he had lumbar paraspinal tenderness, a positive straight leg-raise at 40 degrees on the left and decreased sensation in the L5 dermatome, though reflexes were still intact.

Dr. Arreaza:
That’s a great case. Let’s take a minute and talk about the straight leg raise test. This is a bedside tool we use to assess for lumbar nerve root irritation often caused by a herniated disc. ***Here's how it works: the patient lies supine, and you slowly raise their straight leg. If pain radiates below the knee between 30° and 70°, that suggests radiculopathy, especially involving the L5 or S1 nerve roots. Pain at higher angles is more likely due to hamstring tightness or mechanical strain.

Michael:
Right. So, stepping back: what do we mean by "low back pain"? Broadly, it's any pain localized to the lumbar spine, but it’s often classified by type or cause:

1. Mechanical (like muscle strain or degenerative disc disease),
   
    
2. Radicular (nerve root involvement),
   
    
3. Referred pain (like from pelvic or abdominal organs),
   
    
4. Inflammatory (AS), and
   
    
5. Systemic or serious causes like infection or malignancy.
   
    

Jordan:
In John’s case, we’re thinking radicular pain, most likely from a herniated disc compressing the L5 nerve root. That’s supported by the dermatomal numbness, the leg pain, and that positive straight leg test.

Dr. Arreaza:
Good reasoning. Now, anytime we see back pain, our brains should run a checklist for red flags. These help us pick up more serious causes that require urgent attention. Let’s run through the red flags.

Michael:
Sure. For fracture