Imaging of plantaris friction syndrome

Plantaris friction syndrome is a relatively recently described and clinically under-recognised cause of mid-Achilles tendinopathy. Its pathogenesis is incompletely understood, but may relate to the presence of a compressive tendinopathy between the Achilles and plantaris tendons and resultant inflammation and adhesions within the peritendinous tissues. The role of plantaris tendinopathy in mid-Achilles tendinopathy is still being elucidated, but apparently contradictory findings in the literature potentially reflect different stages of the same pathological process. This article discusses the pathophysiology, clinical presentation, imaging findings, and management of plantaris friction syndrome. Particular emphasis is placed on the imaging findings. Ultrasound and magnetic resonance imaging (MRI) are the primary techniques for imaging the Achilles and plantaris tendons; however, due to spatial and contrast resolution limitations, identification of plantaris friction syndrome can be challenging. Ultrasound tissue characterisation (UTC) is therefore discussed as a useful adjunct to conventional B-mode ultrasound and MRI.