An unusual cause of a painful plantar mass

Anomalous or accessory muscles in and around the foot and ankle have been reported in 8% of the population. Quadratus plantae muscle is one of the medial anomalous muscles in the foot and is a rare cause of heel pain or mass. This muscle has been implicated in tarsal tunnel syndrome. There is exiguous radiological description of quadratus plantae muscle in the literature. We present a case of quadratus plantae muscle presenting as a painful plantar mass and demonstrate its magnetic resonance imaging (MRI) characteristics. We have also reviewed the literature for other medial anomalous muscles around the ankle. This case report shows that MRI can help in establishing the cause of plantar mass and pain in clinically equivocal cases. Most importantly, correlation of imaging with patient's history and clinical examination can prevent unnecessary surgical intervention. The heightened anatomical awareness will assist a general or musculoskeletal radiologist to delineate these anomalous muscles as a cause of painful mass and help in overcoming a clinician's dilemma.