Help with DDX. ?Cortical Desmoid and “bone-within-bone” in the patella.


#1) Thank you to everyone who responded:
Dr. Don Resnick, Dr. Avneesh Chhabra, Dr. Leanne Seeger, Dr. Bill Snearly, Dr. Jeff Clarke, Dr. Sergio Viana, Dr. Carlos Gimenez, Dr. Chris Loupatatzis

The unanimous opinion is a benign cortical desmoid (aka cortical avulsive lesion, distal femoral avulsive cortical defect/irregularities). No follow up needed. As some of you opined, I also agree that the term “Desmoid” is a misnomer and could be confused with a Desmoid tumor and it’s best to use cortical irregularities or avulsive lesion. It’s basically a tug lesion.

Here’s a reference article from Radiopaedia:

radiopaedia.org/articles/cortical-desmoid

Professor Resnick also sent the attached old article on “Distal Femoral Lesions.”

#2) However, even more interestingly, Dr. Resnick observed the following finding:

“ Of interest in your case is the bone-within-bone appearance in the patella with the bright peripheral signal. This relates to hyperemia. It is not specific but can relate to the subacute phase following an injury (although I note there is no history of injury). There is an article by Larry White about 5-8 years ago discussing this finding after injuries but we have seen this with other causes of hyperemia including RSDS and rapidly developing osteoporosis.
Don”

In fact, the pt plays sports and complains of anterior knee pain around the kneecap, although she doesn’t recall any recent injury. Like Dr. Resnick points out, this appearance is most likely due to a subacute injury. RSDS (aka CRPS) is also in the DDX.

Attached: Better images of the patella and the article suggested by Dr. Resnick.

Cheers,
Ray

On May 13, 2021, at 2:19 PM, Ray Hashemi <rhashemi@pacbell.net> wrote:

 Sorry, forgot the history. 12 y/o female w/ knee pain. No recent injury.


Hi OCADers,

What is your differential diagnosis of the lesion in the posterior medial femoral condyle showing some cortical irregularities? I think it looks worse on the coronals than it actually is because of the plane of scanning. Besides a do-not-touch Cortical Desmoid lesion, would you entertain any other possibility? There’s thickening at the insertion of the medial head of the gastrocnemius tendon (which also goes along with a cortical avulsive injury). Should it be followed up?

Thank you,
Ray Hashemi, MD, PhD, FACR

Attached: MRI PD / PD FS and CT