Case 7. Large peroneal tubercle with split tear of peroneus brevis

From Ranjeet Singh, MD, Kirkland, WA, (U. Washington Clinical Faculty)

Clinical History:  A 57 year old woman presented with a 6 month history of progressive lateral ankle pain and swelling. She was previously asymptomatic and gave no history of trauma. Peroneal tenosynovitis was suspected clinically.

Findings: MRI demonstrated a huge peroneal tubercle (no chondral cap was seen to suggest osteochondroma). The inflamed peroneal brevis tendon passes over the anterosuperior surface of the tubercle and shows an extensive longitudinal tear extending to the tendon insertion.

Hypothesis: The coronal images suggest that the peroneal brevis tendon may be undergoing impingement between the enlarged peroneal tubercle and the lateral malleolus.

Questions: Is this combination of findings familiar to anyone? Can the peroneal tubercle hypertrophy from chronic stress (like a Haglund deformity)? Or is this just a "rogue" tubercle slamming the peroneus brevis tendon?

8 images: 3 axial FSE proton density, 2 coronal FSE proton density, 2 axial fat suppressed FSE T2 and 1 sagittal fat supressed FSE T2.