Tenosynovitis of the peroneal tendons due to hypertrophic peroneal tubercle Imaging Findings: • Large volume ofT2-hyperintense fluid signal within the tendon sheath of the peroneal tendons. • Marked marrow edema of the calcaneus with a hypertrophic peroneal tubercle and vertical non-displaced fracture of the tubercle on the Coronal PD fat saturated sequence. • The thickened peroneus brevis lies superior and the peroneus longus inferior to the peroneal tubercle. Case description: • Enlarged peroneal tubercle can impinge the peroneal tendons and result in stenosis tenosynovitis due to chronic friction and increased tension on the tendons. - Thickened tendons with fluid-signal in the sheath. • Can result in bone marrow edema of the calcaneus at the tubercle. +/- adventitial bursitis adjacent to the peroneal tubercle. +/- thickening of the inferior peroneal retinaculum. Differential diagnosis for similar location of pain: • Peroneal tendon subluxation/dislocation or tear. • Talar osteochondral lesions. • Calcaneal stress fracture. Dr. Donald von Borstel @DrvonBorstel #hypertrophic #peroneal #tendons #tubercle #clinical #mri #clinical #Radiology #diagnosis #msk