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These are MR images of a 60-year-old woman

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who has chronic lateral ankle pain, no trauma.

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The main findings involve the peroneal

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compartment, the lateral flexor

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compartment of the ankle, where we see

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fluid distension of the peroneal tendon

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sheath in the retromalleolar portion.

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And then, as we go down, we see change

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in the morphology of the peroneus brevis

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tendon, which is starting to look like this.

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Like a boomerang, we see these curvilinear

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crescentic-like deformity of the tendon as it

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wraps around the peroneus longus tendon, both in

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the retromalleolar and inframalleolar portions.

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This is due to the presence of multiple

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longitudinal split tears that are making the

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tendon adapt to the shape of the peroneus brevis.

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Associated findings that are important to describe

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in the setting of peroneal tendon dysfunction

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are the presence of accessory muscles within the

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peroneal tunnel that may cause overcrowding of the

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tendons and predispose to tearing, so we should

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assess for the presence of peroneal sclerosis.

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In this patient, we're seeing the

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presence of an accessory muscle slip here.

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You can see the tendon as it blends

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with the peroneus brevis, and there is no

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attachment to the lateral calcaneal wall.

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So this is not a peroneal sclerosis.

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This is an accessory slip or low-line slip

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of the peroneus brevis, which is blending or

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merging with the main tendon further down.

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As we go into the inframalleolar region,

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it is important to also describe in our

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report where does the tendon reconstitute.

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So typically we're going to see

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reconstitution of the tendon here by

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the level of the calcaneocuboid joint.

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In this patient, the reconstitution only happens

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just proximal to the inframalleolar region.

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Insertion into the base of the 5th metatarsal.

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Longitudinal images allow us to see the

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extent of the tear, affecting both the

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retromalleolar and the inframalleolar

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components and just reconstitution immediately

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proximal to the insertion at the base

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of the fifth metatarsal in this patient.

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The peroneus longus allow us to have an

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internal comparison of what is normal.

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So, you can see that the tendon has

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homogeneous low signal intensity and its

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caliber is preserved throughout its course.

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So, in summary,

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Longitudinal split tear of the Perone brevis

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affecting both the retromolar and infra

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malleolar portions associated with peroneal

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tinosynovitis and reconstitution just proximal

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to the insertion at the fifth metatarsal base.