Remote ganglion cyst and Hoffa impingement

Case contributed by Dr Matt Skalski

Presentation

Continued knee pain. Follow up medial knee mass noted one year prior.

Patient Data

Age: 50 years
Gender: Female

Within the subcutaneous fat overlying the proximal medial tibia there is a cystic mass with fluid-like signal which demonstrates peripheral and septal enhancement. There is minimal edema surrounding this lesion. A small, fluid-signal tract can be seen coursing from the inferior aspect of the lesion to the infrapatellar bursa. This lesion appears unchanged from the exam one year prior. 

Fluid is observed within the deep infrapatellar bursa with a moderate amount of adjacent edema in Hoffa's fat pad which is new from the prior exam, and appear to be related to fluid dissecting from the ACL/anterior root of the medial meniscus into this space and then on to the previously described fluid collection.

There is a minimal amount of edema deep to the distal iliotibial (IT) band. 

Intrasubstance degeneration of posterior horn of the medial meniscus is noted, without a surface tear. 

The findings described in the previous section are outlined here with blue arrows as described below.

  • the fluid tract from the cyst to the joint space is indicated by the blue arrowhead
  • the intrasubstance degeneration of the posterior horn of the medial meniscus is indicated by the blue arrow
  • the edema deep to the IT band is indicated by the open blue arrow
  • the edema in Hoffa's fat pad is indicated by the blue tailed arrow. The fluid within the infrapatellar bursa is indicated by the blue squiggly arrow

Case Discussion

Occasionally, ganglion cysts may not be juxtaarticular in location, tracking distant from the joint to arise in a remote location as seen here. In these instances a tract to the joint space should be searched for, but a connection to the cyst is not always found. Absence of a connection does not exclude the diagnosis of a ganglion cyst. 

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