ACL ganglia and mucoid degeneration

Over the last few years, we have been increasing identifying patients with abnormal ACLs that show features suggestive of mucoid degeneration of intra-ligamentous ganglion cysts. As seen in this T2W image the ACL in mucoid degeneration is abnormally thickened and shows variable increased signal. Near the femoral insertion on this image, there is a multi-loculated cyst, which may represent a ganglion cyst.

A couple of the cases I had seen were reported by Dr. Abhay Narvekar in Arthroscopy. Five cases seemed like a big number, until this article that was published in the May issue of AJR, that deals with 74 examinations that met the criteria for either mucoid degeneration (24%)or discrete ganglia (76%). 35% had features of both.

For those reporting MRI knees on a regular basis, this article is a must to understand these two related entities.