Mucoid degeneration can affect both the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL). Mucoid degeneration is often confused with ACL tears and this post looks at the main MRI features of ACL and PCL mucoid degeneration that will help to differentiate from tears.



  • The ACL is enlarged and hyperintense but there is continuity of fibres and normal alignment.

  • The enlargement is more prominent proximally giving it the appearance of a celery stalk (celery stalk sign of ACL mucoid degeneration).



This is a characteristic appearance of ACL mucoid degeneration. Look for, 

  • Expanded hyperintense ACL.
  • Fibres are continuous.
  • Alignment of fibres is normal.


  • Intra ligamentous cysts are commonly found in mucoid degeneration of the ACL.


  • Size can be variable from small cysts like in this image to larger ones we will see next.


  • Look for T2 hyperintense cystic changes in the ACL.


  • Cysts can extend from the ACL into the bony attachments at the tibia or femur.


  • Look for cystic change of variable size at the femor and tibia at the attachment site.


  • Intraligamentous cysts can also extend into the adjacent soft tissue.

knee ligament mucoid degen acl pcl mcl radiology radedasia


  • It's not just the ACL that undergoes mucoid degeneration.


  • The PCL can also be involved but it's less common.


  • Mucoid degeneration of the PCL can be in conjunction with the ACL or on its own.


  • Look for the same findings discussed for the ACL to make the diagnosis.


  • Ligament thickening.

  • "Celery stalk" sign.

  • Increased T2 Signal intensity.

  • Preserved fibres which are in continuity.

  • Normal alignment of the ACL or PCL.

  • Intra ligamentous cysts of variable size.

  • Intra osseous extension of the cysts.

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