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Remote Fellowship – Foot & Ankle Fundamentals – 11/2/2020

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Peroneus Longus Tear 

Case Discussion

Peroneal tendon pathology is a common cause for lateral ankle pain after capsuloligamentous injuries. Peroneal tendinopathy/tearing occurs most frequently due to overuse/chronic repetitive microtrauma and is less commonly the result of acute trauma from inversion injuries.

Anatomical anomalies play an important role in pathogenesis. The major anatomical variants that may contribute to peroneal tendon pathology include: os peroneum, a low lying peroneus brevis muscle belly, laxity of the superior peroneal retinaculum, hypertrophy of the peroneal tubercle, a flat or convex retromalleolar sulcus of the fibula, and the presence of the peroneus quartus muscle. The peroneus quartus muscle typically originates from the peroneus brevis muscle and has a variable insertion distally at the retrotrochlear eminence or the peroneal tubercle. When present, it may cause overcrowding and friction among the peroneal tendons in the retromalleolar groove.

When imaging the peroneal tendons on MRI, it is important to be wary of the “Magic Angle Effect”. This is an artifact that occurs with sequences having shorter TE values (including T1-weighted and PD sequences) when the tendons are imaged at approximately 55 degrees relative to the main magnetic field. When this happens, the tendons will appear hyperintense, thus potentially being mistaken for tendinopathy. This artifact can be minimized by positioning the patient’s ankle in plantar flexion.

Peroneus longus tendon tears are uncommon relative to peroneus brevis tears. They are most often associated with underlying chronic hypertrophic tendinopathy (versus attritional/atrophic peroneus brevis tendon tears).

Peroneus longus tears commonly occur around an accessory ossicle (os peroneum). The tendon typically ruptures just distal to or through the accessory ossicle within the cuboid groove. 

Key Images

Peroneus longus tear in a 63-year-old man complaining of pain and swelling of the right lateral ankle for 6 months.

A. Sagittal T2 FS image of the right ankle shows thickening of the juxta- and inframalleolar portions of the peroneus longus tendon and a linear area of high intensity signal representing tendinopathy and complex longitudinal tearing (red arrow).
B. Axial PD FS image shows tenosynovitis surounding peroneus brevis (green arrow) and surrounding the peroneus longus tendon (red arrow) and complex interstitial tearing of the peroneus longus tendon (yellow arrow).
C. Axial T1 image shows a large peroneocalcaneal tubercle with spuring arising from the lateral calcaneus (red arrow).


  1. Scanlan RL, Gehl RS. Peroneal tendon injuries. Clin Podiatr Med Surg 2002; 19(3):419-431
  2. Taljanovic MS , Alcala JN, Gimber LH, Rieke JD, Chilvers MM, Latt LD. High-resolution US and MR imaging of peroneal tendon injuries. RadioGraphics 2015; 35:179-199