Cortical desmoid

Case contributed by Yasser Asiri
Diagnosis almost certain


Presented with left knee pain and suspicion of bone lesion.

Patient Data

Age: 17 years
Gender: Male

Irregularity of the medial aspect of the left femoral metaphysis without evident soft tissue abnormality.

Left knee


CT images clearly show the cortical irregularity and the spiculated periosteal bone formation at the posteromedial aspect of the distal femoral metaphysis; more specifically, at the attachment of the medial head of the gastrocnemius muscle and adductor magnus tendon. 

Left knee


Mild edema at the area of cortical irregularity and to a lesser extent the attachment of the tendons is seen. No underlying bone marrow edema or destructive bone marrow lesions are seen. Small Baker's cyst is seen.

Case Discussion

Cortical desmoid is considered a "tug lesion" located in the posteromedial aspect of the distal femoral metaphysis seen in an immature skeleton. It is postulated to be due to abnormal bone stresses applied by medial head of gastrocnemius origin and the adductor magnus tendon insertion. The typical location and imaging features are usually sufficient to reach a confident diagnosis of this condition.

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