Plantaris tendon and association with mid-portion Achilles tendinopathy. Is the plantaris tendon a contributing factor in mid-portion Achilles tendinopathy?

Plantaris tendon is implicated in some cases of load-resistant Achilles tendinopathy. The tendon courses close to the medial Achilles tendon mid-portion prior to insertion onto the medial calcaneus, although there is variation in course and insertion. Clinical suspicion of plantaris involvement includes persistent medial Achilles pain unresponsive to a rehabilitation programme and imaging revealing a thickened plantaris tendon and/or focal medial Achilles tendinosis. Potential mechanisms include compression or shearing forces between the plantaris and Achilles tendons. Initial treatment should consist of a modified loading programme avoiding end-range loading. Resistant cases may be amenable to surgical excision of the plantaris demonstrating good clinical outcomes in the short and long term, although the evidence is limited to case series. Percutaneous methods show promise but require further evaluation.