MRI of the Knee: With or Without Contrast
MRI of the knee should be performed WITHOUT contrast for most clinical indications, as recommended by the American College of Radiology (ACR) Appropriateness Criteria for chronic knee pain. 1
Recommended Protocol for Knee MRI
Standard Protocol (Non-Contrast)
- MRI without IV contrast is the standard protocol for evaluating most knee pathologies including:
- Meniscal tears (sensitivity 96%, specificity 97%) 2
- Ligament injuries (ACL, PCL, collateral ligaments)
- Cartilage defects
- Bone marrow edema
- Osteochondral lesions
- Joint effusions
- Loose bodies
When to Use Contrast
Contrast-enhanced MRI is rarely indicated for routine knee imaging. 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
Limited indications for contrast may include:
- Suspected synovial pathology (synovitis, PVNS)
- Infection evaluation
- Certain tumor assessments
- Post-surgical evaluation when non-contrast images are equivocal
Technical Considerations
Optimal Imaging Protocol
- Three orthogonal imaging planes (axial, coronal, sagittal) 3
- Basic protocol must include:
- T2-weighted fluid-sensitive sequences
- T1-weighted sequences
- Fat-suppressed sequences for better visualization of bone marrow edema
Sequence Recommendations
- Proton density (PD) sequences with fat suppression for meniscal evaluation
- T2-weighted fat-suppressed sequences for ligament and bone marrow assessment
- T1-weighted sequences for anatomical detail and alignment
Clinical Decision Algorithm
Initial Assessment:
- Begin with plain radiographs to rule out fractures and assess alignment 4
MRI Protocol Selection:
- For most knee conditions → Non-contrast MRI
- For suspected internal derangement → Non-contrast MRI
- For suspected infection or synovial pathology → Consider contrast-enhanced MRI
Special Considerations:
- For cartilage-specific evaluation → Consider adding 3D sequences to routine protocol for improved specificity 5
- For post-operative evaluation → Non-contrast MRI with metal artifact reduction techniques if hardware present
Pitfalls to Avoid
- Overreliance on contrast when not indicated
- Inadequate imaging planes (all three orthogonal planes are necessary)
- Misinterpretation of normal variants as pathology
- Failure to correlate with clinical findings
Evidence Quality Assessment
The recommendation for non-contrast MRI is supported by high-quality evidence from the ACR Appropriateness Criteria, which synthesized 66 references including 28 well-designed or good-quality studies published between 2000-2018 1. This recommendation aligns with the European Society of Skeletal Radiology (ESSR) practice recommendations, which emphasize standardized non-contrast protocols for knee MRI 3.
Adding 3D sequences to standard non-contrast protocols has been shown to improve diagnostic performance for cartilage lesions, particularly specificity, without requiring contrast administration 5.