Updated: 3/13/2020

Knee Imaging

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https://upload.orthobullets.com/topic/3004/images/segond fx_moved.jpg
https://upload.orthobullets.com/topic/3004/images/XR - Pellegrini-Stieda_moved.jpg
https://upload.orthobullets.com/topic/3004/images/osteochondral lesion xray.jpg
https://upload.orthobullets.com/topic/3004/images/patella altal.jpg
https://upload.orthobullets.com/topic/3004/images/patella baja.jpg
https://upload.orthobullets.com/topic/3004/images/fairbanks knee.jpg
https://upload.orthobullets.com/topic/3004/images/screen_shot_2017-10-27_at_7.30.25_pm.jpg
  
High yield findings

Finding
Importance
 Images
Segond sign  Small lateral tibial avulsion fracture that indicates a ACL tear
Reverse Segond sign
Small medial tibial avulsion fracture that indicates a PCL tear
Arcuate sign Fibular head avulsion fracture that indicates a PLC injury
Pellegrini Stieda sign Medial femoral condyle avulsion fracture that indicates a chronic MCL injury
Patella alta Patellofemoral pathology
Patella baja Arthrofibrosis
Fairbanks changes  DJD - post meniscectomy (square condyle, peak eminences, ridging, narrowing)
Lateral MFC lesion OCD
Crescent-shaped MFC lesion Spontanous osteonecrosis of the knee (SONK)
Square lateral femoral condyle, cupped lateral tibial plateau, hypoplastic lateral tibial spine Discoid meniscus
3 sagittal MRI images Discoid meniscus  
Bipartite patella
Must differentiate from fracture
 

Radiographic
  • Standard Radiographs
    • Weightbearing 
      • preferred for evaluation of joint space 
    • 45 degree PA flexion view (Rosenberg view)
      • best for early tibiofemoral arthritis, posterior wear 
    • Merchant or sunrise view 
      • to evaluate patellofemoral space, tilt, and alignment  
  • Stress Radiographs
    • Varus-valgus stress radiographs
      • two diagnostic indications
        • physeal fractures in children
        • MCL / LCL injuries
    • Posterior stress radiographs
      • isolated PCL injury (10-12 mm posterior displacement)
      • PCL and PLC injury (>12 mm posterior displacement)
MRI
  • Views
    • sagittal  
      • evaluate menisci, cruciates, cartilage, extensor mechanism
    • coronal 
      • evaluate menisci, cruciates, collaterals, cartilage
    • axial 
      • evaluate patellofemoral joint, cruciates, popliteal fossa
  • Sequences
    • T1
      • water dark, fat bright
      • best for showing anatomy, but not pathology
    • T2 
      • fat dark, water bright
      • well suited for imaging edema and pathology  
    • STIR (Short T1 Inversion Recovery)
      • fat suppression technique
      • improved quality imaging in the presence of orthopedic prostheses
  • Excellent for
    • meniscal injury
      • medial meniscal extrusion >3mm is associated with severe meniscal degeneration, a large meniscal tear, or tear of the root
      • radial meniscal tears are more common in patients following prior meniscal surgery (32% prevalence of radial meniscal tears in post-op knees compared to 14% in patients without prior surgery)
      • 3.0 T MRI has accuracy, sensitivity, and specificity of >90% for detecting medial and lateral meniscus tears
    • ligament tear
      • increased signal intensity, thickening, and cysts within and adjacent to ACL are common findings, and clinically insignificant (no instability)
    • bone bruise
      • near sulcus terminalis
      • osteochondral injury
    • PLC corner injuries
      • can routinely visualize LCL and popliteus tendon with MRI, other structures are more rarely seen
      • edema posterior to popliteus tendon can indicate an injury to the underlying structures of the PLC 
 Ultrasound
  • Excellent for   
    • fluid collections
      • useful to evaluate bursae and fluid collections about the knee
    • arthrofibrosis
      • effective in detecting arthrofibrosis of the knee following TKA
      • key findings for arthrofibrosis are synovial thickening and neovascularity 
 

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Questions (1)

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(OBQ07.100) Which of the following radiographic views is most sensitive for detecting knee joint degenerative changes? Review Topic | Tested Concept

QID: 761
1

Non-weight-bearing AP

0%

(4/1796)

2

Weight-bearing AP

15%

(278/1796)

3

Non-weight-bearing PA in 45 degrees flexion

1%

(19/1796)

4

Weight-bearing PA in 45 degrees flexion

82%

(1479/1796)

5

Merchant

1%

(12/1796)

L 2 D

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