Tibial tunnel cysts may be a complication of ACL reconstruction surgery. The communicating type maintain a connection with the knee joint space, as we see in this case. This is presumed to be caused be either incomplete attachment of the graft to the bony tunnel or graft microtrauma.

It is important to differentiate non-communicating from communicating tibial tunnel cysts and convey this in radiology reports, as the conditions are managed differently. Please see related article for further details.