Anatomy Msk · Year 1 · from Anatomy Msk
Case 1: Lumbar Strain with Paraspinal Muscle Spasm
Clinical Image
Source: Wikimedia Commons - Lumbar MRI - CC BY-SA 3.0
Case Presentation
A 35-year-old office worker presents with acute onset of lower back pain that began yesterday while moving furniture. He describes the pain as a dull ache across his lower back that increases with movement and is relieved by lying flat. He denies any radiation of pain into his legs, numbness, tingling, or weakness. There is no history of trauma, fever, weight loss, or bowel/bladder dysfunction. Physical examination reveals paravertebral muscle tenderness and palpable spasm bilaterally at the L4-L5 level. Range of motion is limited in all directions due to pain and guarding. Straight leg raise is negative bilaterally. Neurological examination including strength, sensation, and reflexes in the lower extremities is completely normal. Given the lack of red flag symptoms and normal neurological examination, imaging is deferred per clinical guidelines. The patient is diagnosed with acute mechanical low back pain from lumbar strain and paraspinal muscle spasm. He is treated with NSAIDs, muscle relaxants, and advised to continue gentle activity as tolerated, avoiding bed rest. Physical therapy is prescribed focusing on core strengthening and proper body mechanics.
Key Learning Points
- The erector spinae group (iliocostalis, longissimus, spinalis) are primary extensors of the vertebral column
- Paraspinal muscles can go into protective spasm following injury, limiting motion and causing pain
- Mechanical low back pain is the most common cause of back pain and has a favorable natural history
- Red flag symptoms (cauda equina syndrome, progressive neurological deficit, malignancy, infection) require urgent evaluation
- Imaging is not indicated for acute low back pain without red flags in the first 4-6 weeks