For persistent knee pain after a knee injury, do you order an MRI (Magnetic Resonance Imaging) with or without contrast?

MRI Without Contrast is the Appropriate Choice for Persistent Knee Pain After Injury

For persistent knee pain after a knee injury, MRI without contrast is the most appropriate imaging choice to evaluate soft tissue and osseous structures while minimizing unnecessary radiation and contrast exposure. 1

Initial Evaluation Algorithm

1. First step: Plain radiographs

   • Should include at least one frontal projection (anteroposterior, Rosenberg, or tunnel view)
   • Tangential patellar view
   • Lateral view of the affected knee

2. If radiographs are normal or show joint effusion but pain persists:

   • Proceed to MRI without contrast

3. If radiographs show specific findings:

   • Signs of prior osseous injury (Segond fracture, tibial spine avulsion)
   • Osteochondritis dissecans (OCD)
   • Loose bodies
   • History of cartilage or meniscal repair
   • → MRI without contrast remains the appropriate next step

Why MRI Without Contrast is Superior

MRI without contrast provides comprehensive evaluation of:

• Meniscal tears (common after knee injury)
• Ligament injuries (ACL, PCL, MCL, LCL)
• Bone marrow edema and subchondral insufficiency fractures
• Cartilage damage
• Joint effusions and synovitis
• Presence or rupture of popliteal cysts 1

When Contrast Might Be Considered (Rare Exceptions)

Contrast-enhanced MRI is generally not indicated for evaluation of persistent knee pain after injury. According to the ACR Appropriateness Criteria, "MRI without and with IV contrast is not usually indicated to evaluate patients with signs of prior (chronic) osseous knee injury." 1

The only rare situations where contrast might be considered include:

• Suspected infection
• Inflammatory arthropathy
• Synovial proliferative disorders
• Post-surgical evaluation where scar tissue vs. recurrent pathology needs differentiation

Important Clinical Considerations

• Bone marrow lesions (BMLs) seen on MRI correlate with knee pain intensity and are best visualized without contrast 1
• New or increasing BMLs are associated with increased knee pain, especially in males or patients with family history of osteoarthritis 1
• Joint effusions detected on MRI significantly correlate with pain severity in knee osteoarthritis 2
• MRI can identify subchondral insufficiency fractures earlier than radiographs, with radiographs often initially normal 1

Common Pitfalls to Avoid

1. Ordering contrast unnecessarily:

   • Adds cost, procedure time, and risk of adverse reactions
   • Rarely provides additional diagnostic information for post-traumatic knee pain

2. Relying solely on radiographs:

   • May miss soft tissue injuries and early cartilage damage
   • MRI is more sensitive for detecting early cartilage degeneration 3

3. Overlooking deep MCL injuries:

   • Patients with persistent medial joint pain following MCL sprain should have MRI to confirm diagnosis and localize the lesion within the deep MCL 4

4. Ordering CT instead of MRI:

   • CT is primarily useful for better delineation of fractures in acute trauma
   • MRI is superior for evaluating cartilage, menisci, and ligaments when arthroscopy is contemplated 5

By following these evidence-based guidelines, clinicians can optimize diagnostic accuracy while minimizing unnecessary testing and contrast exposure in patients with persistent knee pain after injury.