What type of MRI should I order for a patient with a suspected meniscal or ligament injury in the right knee, with or without contrast or arthrogram?

MRI Without IV Contrast is the Appropriate Choice for Suspected Meniscal or Ligament Knee Injury

MRI without IV contrast is the most appropriate imaging study for evaluating suspected meniscal or ligament injuries of the knee, as it provides excellent visualization of soft tissue structures without requiring contrast or arthrography. 1

Initial Imaging Approach

• Begin with plain radiographs of the knee to rule out fractures before proceeding to advanced imaging 1
• For suspected internal derangement (meniscal or ligamentous injuries) with negative radiographs, MRI without IV contrast should be the next imaging study 1
• MRI without contrast has superior contrast resolution and multiplanar imaging capability for evaluating soft tissue injuries 1

Why MRI Without Contrast is Preferred

• MRI without IV contrast demonstrates excellent sensitivity and specificity for detecting:

  • Meniscal tears (85-100% sensitivity, 69-88% specificity) 2, 3
  • ACL injuries (86-90% sensitivity, 91-94% specificity) 2, 3
  • PCL injuries (100% sensitivity, 95-100% specificity) 2, 3

• MRI accurately depicts:

  • Joint effusions and synovitis 1
  • Bone marrow contusions and occult fractures 1
  • Articular cartilage damage 1, 4
  • Extent of meniscal and ligamentous injuries 4, 5

When Other Imaging Modalities Are Indicated

• MR arthrography is not routinely used for initial evaluation of acute knee trauma or suspected meniscal/ligamentous injuries 1
• CT knee is primarily useful for:
  • Evaluating fractures, especially tibial plateau fractures 1
  • Patellofemoral anatomy in cases of chronic subluxation 1
• CT arthrography may be considered as an alternative to MRI in specific cases where menisci and articular cartilage need evaluation but MRI is contraindicated 1

Clinical Pearls and Pitfalls

• Avoid ordering MRI with contrast for routine meniscal or ligamentous injuries as it provides no additional diagnostic value over non-contrast MRI 1
• Be aware that meniscal tears are often incidental findings in older patients (majority of people over 70 years have asymptomatic meniscal tears) 1
• In cases of significant trauma or suspected knee dislocation, vascular assessment may be necessary (CTA or MRA) due to risk of popliteal artery injury 1, 6
• MRI has largely replaced diagnostic arthroscopy as the initial diagnostic tool, though arthroscopy remains the gold standard for definitive diagnosis 2, 7

Algorithm for Knee Injury Imaging

1. Obtain plain radiographs first to rule out fractures 1
2. If radiographs are negative or show only joint effusion, proceed to MRI without contrast 1
3. If MRI shows equivocal findings and clinical suspicion remains high, consider arthroscopy for both diagnosis and treatment 2, 7
4. Only consider MR arthrography or CT arthrography in specific cases where standard MRI is contraindicated or unavailable 1

MRI without IV contrast remains the imaging modality of choice for evaluating meniscal and ligamentous injuries of the knee, providing excellent diagnostic accuracy while avoiding the risks associated with contrast agents or invasive procedures 2, 4.