What is the diagnosis for a 36-year-old female presenting with left lower back pain, specifically at the Sacroiliac (SI) joint, radiating to the buttock, with tender back mice, spasmodic lumbar and mid-back contractions, and a positive Straight Leg Raise (SLR) test at 30-40 degrees?

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Last updated: February 24, 2025 • View editorial policy

Differential Diagnosis for Lower Back Pain

Single Most Likely Diagnosis

  • Sacroiliac Joint Dysfunction: The patient's symptoms of lower back pain localized to the left SI joint, radiating to the buttock, and tenderness over the SI joint are classic for SI joint dysfunction. The presence of back mice (small, tender, palpable innocuous-appearing skin lesions) and the patient's description of a "fist locked up" in her lower back also support this diagnosis.

Other Likely Diagnoses

  • Lumbar Facet Joint Syndrome: The patient's symptoms of lower back pain with spasmodic moments and painful contractions could be related to lumbar facet joint syndrome. The tenderness over the back and the presence of back mice also support this diagnosis.
  • Piriformis Syndrome: The patient's symptoms of pain radiating to the buttock and the positive SLR (Straight Leg Raise) test at 30-40° could be indicative of piriformis syndrome, which occurs when the piriformis muscle irritates the sciatic nerve.
  • Musculoskeletal low back pain: The patient's symptoms of lower back pain with spasmodic moments and painful contractions could also be related to musculoskeletal low back pain, which is a common condition characterized by strain or injury to the muscles, ligaments, or tendons in the lower back.

Do Not Miss Diagnoses

  • Cauda Equina Syndrome: Although less likely, cauda equina syndrome is a serious condition that requires prompt medical attention. It is characterized by compression of the nerve roots in the lower spine, which can cause severe back pain, sciatica, and loss of bladder and bowel control.
  • Spinal Infection or Abscess: Infection or abscess in the spine can present with severe back pain, fever, and neurological symptoms. Although rare, this diagnosis should not be missed as it requires prompt medical attention.
  • Fracture or Osteoporotic Compression Fracture: A fracture or osteoporotic compression fracture can present with sudden onset of severe back pain and should not be missed, especially in patients with risk factors for osteoporosis.

Rare Diagnoses

  • Ankylosing Spondylitis: A chronic inflammatory disease that can cause lower back pain and stiffness, ankylosing spondylitis is a rare condition that should be considered in patients with persistent back pain and stiffness.
  • Osteoid Osteoma: A rare benign tumor that can cause severe back pain, osteoid osteoma is a diagnosis that should be considered in patients with persistent back pain that is worse at night and improves with NSAIDs.

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.