Anterior cruciate ligament ganglion cyst

Last revised by Dr Henry Knipe on 03 Feb 2021

Anterior cruciate ligament (ACL) ganglion cysts, commonly referred to simply as ACL cysts, along with ganglion cysts arising from the alar folds that cover the infrapatellar fat pad, make up the vast majority of intra-articular ganglion cysts of the knee.

Anterior cruciate ligament ganglion cysts are uncommon, with the prevalence reported to be between 0.3-1.3% of knee MRIs, and are usually incidental findings.

ACL ganglion cysts have non-specific symptoms including pain, locking, clicks, and/or reduced knee extension 8.

Anterior cruciate ligament ganglion cysts are histologically identical to the ganglion cysts seen elsewhere, most commonly around the wrist. They comprise mucoid material surrounded by a pseudocapsule 6.

The pathogenesis remains controversial, with two theories being favored:

  • sequelae of ACL mucoid degeneration
  • herniation of synovial tissue through a defect in the joint capsule or tendon sheath

MRI is the gold standard for diagnosis and has higher sensitivity compared to standard anterior portal approach arthroscopy since an intraligamentous lesion may not be apparent externally (ligament may appear normal arthroscopically) 6. A posterior approach will allow the arthroscopist to detect changes by probing the ligament and will allow potential aspiration of the cysts.

In one of the largest imaging studies of ACL ganglion cysts, Bergin et al used two out of three criteria for diagnosis 2:

  • T2 signal within the ACL, hyperintense to joint fluid
  • lobulated (or multiloculated) lesion margin
  • mass effect on ligament fibers

Often there is some irregularity to the bone subjacent to the tibial insertion.

Ganglion cysts of the anterior cruciate ligament were first described by Caan in 1924 7.

Consider

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Cases and figures

  • Case 1
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  • Case 2
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  • Case 3: with mucoid degeneration
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  • Case 4
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  • Case 5
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  • Case 6
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  • Case 7
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  • Case 8: with mucoid degeneration
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