Knee protocol (MRI)

MRI knee protocol comprises a group of MRI sequences to routinely assess the knee for internal pathologies such as meniscal, ligament and cartilage injury.

As with most MR joint imaging, PD weighted sequences with and without fat-saturation are usually the mainstay. Often a T2 FS sequence is included as a replacement to PD FS in one plane, typically coronal. A T1 weighted sequence is usually included in one plane to facilitate the assessment of any incidental marrow or soft-tissue lesions.

Note: This article is intended to outline general principles. Protocol specifics will vary depending on MRI hardware and software, radiologist and referrer preference, patient factors and time constraints.

Sequences

A standard MRI knee protocol for internal derangement such as meniscal tear might look something like:

• PD weighted
  • plane: sagittal, coronal, axial (optional)
  • technique: PD fast-spin echo
  • slice thickness: 3 or 4 mm
  • purpose: detailed anatomy, fat helps to outline structures, good differentiation between fluid (high signal), hyaline cartilage (intermediate signal) and ligaments/tendons/menisci (low signal) 
• PD weighted (fat-saturated)
  • plane: sagittal, coronal (optional), axial (optional)
  • technique: PD FS fast-spin echo 
  • slice thickness: 3 or 4 mm
  • purpose: best sagittal sequence for meniscal tear detection, fat-saturation helps reveal fluid such as marrow edema, fat pad edema, bursae, parameniscal cysts  
• T2 weighted (fat-saturated)
  • plane: coronal, axial (optional)
  • technique: T2 FS fast-spin echo
  • slice thickness: 3 or 4 mm
  • purpose: best coronal sequence for meniscal root tear detection, fat-saturation helps reveal fluid such as marrow edema, fat pad edema, bursae, parameniscal cysts  
• T1 weighted
  • plane: at least one, often axial or coronal
  • sequence:  T1 fast-spin echo
  • slice thickness: 3 or 4 mm
  • purpose: to characterize T1 characteristics of any incidental bone or soft-tissue lesion