Anterior cruciate ligament tear

Radswiki et al.

Anterior cruciate ligament (ACL) tears are the most common knee ligament injury encountered in radiology practice.

Pathology

The ACL is the most commonly disrupted ligament of the knee, especially in athletes who participate in sports that involve rapid starting, stopping, and pivoting (e.g. soccer, basketball, tennis, netball and snow skiing).

Associations

Radiographic features

An avulsion of the tibial attachment may be seen in younger patients.

Plain radiograph

Features are non-specific but can include: 

CT arthrography

Considered to have high specificity and sensitivity in detecting ACL disruption 6. CT is helpful in characterising the avulsion bone fragment when it is present. 

MRI

Imaging of ACL tears should be divided into primary and secondary signs.

Primary signs are those that pertain to the ligament itself. Secondary signs are those which are closely related to ACL injuries.

Primary signs
  • swelling
  • increased signal on T2 or PD FS
  • fibre discontinuity
  • change in the expected course of ACL: ACL angle that is less steep than Blumensaat's line: when drawing a line in the course of a normal ACL on the sagittal image the angle should be as steep or steeper than the intercondylar roof, so the apex is pointing posteriorly. If the ACL is less steep than the intercondylar roof (i.e. the apex of the angle points anteriorly) means that ACL is completely torn and collapsed

ACL tears typically occur in the middle portion of the ligament and appear as discontinuity of the ligament or abnormal contour. The signal of the ACL can be more hyperintense on T2. If the angle is still normal and there is a hyperintense signal, a partial rupture is more likely than a complete rupture.

Secondary signs

Secondary signs include:

Related video

Knee pathology

The knee is a complex synovial joint that can be affected by a range of pathologies:

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Article information

rID: 12490
Section: Staging
Tags: knee, refs
Synonyms or Alternate Spellings:
  • Anterior cruciate ligament rupture
  • ACL rupture
  • Tear of ACL
  • Tearing of ACL
  • Rupture of ACL
  • Tear of anterior cruciate ligament
  • ACL tear
  • ACL sprain
  • Anterior cruciate ligament tears
  • Anterior cruciate ligament ruptures
  • ACL tears
  • ACL tearing

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Cases and figures

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    ACL tear
    Figure 1: Illustration - ACL tear mechanism
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    ACL sprain - SAG
    Case 1: sprain
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    ACL avulsion
    Figure 2: Illustration - ACL avulsion fracture
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    Case 2: incomplete tear
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    Torn ACL, full th...
    Case 3: complete tear
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    Case 4: complete tear
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    Segond fracture
    Case 5: with Segond fracture
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    Case 6: complete tear with concurrent MCL tear
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    Case 7: ACL avulsion injury
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    PD FS sagittal ob...
    Case 8: ACL graft tear
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     Case 9
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    Case 10
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    Case 11
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    Case 12: complete ACL tear
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    Case 13: partial disruption - anteromedial bundle
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    The ACL and PCL a...
    Case 14: post dislocation
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