Spondylolysis vs. Spondylolisthesis


  • Defect or stress fracture of the pars interarticularis
  • May be unilateral or bilateral
  • Most common location is L5 of the lower lumbar spine
  • X-rays: AP, lateral, and oblique views
  • “Scottie Dog” sign on x-ray (fracture site is the collar)
  • Seen on posterior oblique view of the lumbar spine
  • Head of Scottie Dog: superior articular process
  • Neck of Scottie Dog: pars interarticularis
  • Body of Scottie Dog: lamina and spinous process
  • Legs of Scottie Dog: inferior articular processes
  • Back pain may be elicited with lumbar extension
  • Management: rest and rehabilitation program
  • Risk of progression to spondylolisthesis (displacement)


  • Anterior slippage of a lumbar vertebra over another
  • May be unilateral or bilateral
  • Usually occurs due to bilateral defects or fractures of the pars interarticularis
  • Most common location is L5-S1
  • Back pain with lumbar extension
  • Pain often radiates to buttocks or posterior legs
  • Paresthesias
  • X-rays: AP, lateral, and oblique views
  • Lumbar vertebra slippage is best seen on lateral view
  • Meyerding classification system grades the severity of slippage
  • Grade I: ≤ 25%
  • Grade II: 26-50%
  • Grade III: 51-75%
  • Grade IV: 76-100%
  • Grade V: > 100% (spondyloptosis)
  • Management: rest, consider bracing
  • Surgical consultation if neurologic involvement, high grade slippage, or failed medical management