Presentation
Pain and swelling of the lateral ankle below the lateral malleolus.
Patient Data
There is a longitudinal split tear involving the peroneus brevis tendon. In addition, there is a partial tear involving the peroneus longus tendon just below the lateral malleolus evident by fibrous discontinuity. There is significant thickening and intermediate signal intensity of peroneus brevis tendon and peroneus longus tendon with surrounding free fluid in keeping with severe tenosynovitis. There is underlying bone marrow edema seen at the lateral aspect of the calcaneal bone at peroneus tubercle with osteophyte formation likely reactive to the adjacent tenosynovitis. There is significant soft tissue edema at the lateral and the dorsal aspect of the foot.
Bone marrow edema at the base of the fifth metatarsal at the attachment of the peroneus brevis suggestive of enthesopathy. There is fatty atrophy with denervation changes involving the extensor digitorum brevis muscle. Foot muscles also demonstrate decrease in muscle bulk, however, no fatty degeneration or edematous changes seen. Maintained alignment of the visualized joint spaces. The rest of the visualized ligaments and tendons appear unremarkable. Minimal joint effusion in the ankle joint.
Case Discussion
Peroneus tendinopathy ranges from peroneus brevis tendonosis which manifested by tendon substance thinning giving the shape of boomerang and then progresses to longitudinal split tear where the peroneus longus tendon is interposed between the two segments of the peroneus brevis tendon. This case additionally shows the secondary signs of tendinopathy including a thickened tendon retinaculum, bone marrow edema of the adjacent bone, and reactive bone spur formation.
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