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Clinical History:
12 year old female ballet dancer with slowly progressive knee pain, aggravated with flexion.
Diagnosis:
Cortical desmoid (distal femoral cortical irregularity) with a partial tear of the medial head of the gastrocnemius muscle at its origin.
MR Technique:
3T (Siemens Verio) 15 channel knee coil; Image 1: Axial T2* Gradient (TR/TE 833/23 ms, slice thickness 3 mm, scan time 3 min 45 sec); Image 2: Sagittal T2 (TR/TE 2800/81 ms, slice thickness 2 mm, scan time 1 min 42 sec); Image 3: Sagittal STIR (TI 220 ms, TR/TE 4700/34 ms, slice thickness 3 mm, scan time 3 min 42 sec).
Imaging Findings:
Cortical desmoid at the origin of the medial head of the gastrocnemius muscle is seen in all the above images. A partial tear of the origin of the gastrocnemius muscle shows surrounding edema on the sagittal STIR image. Edema in the adjacent bone seen on STIR images is due to acute stress reaction.
