Unilateral Accessory Plantaris Muscle: A Rare Anatomical Variation with Clinical Implications

Abstract

Plantaris, a small muscle with its long slender tendon, is of interest not only from anatomical but also from phylogenetic view point. It is regarded as vestigial in man, believing that, with assumption of an erect posture, the tendon lost its original insertion into plantar aponeurosis and gained a secondary calcaneal attachment. The muscle is known to exhibit variations but there are few reports on the existence of complete duplication of plantaris. During the routine dissection for the undergraduate medical students we encountered unilateral accessory plantaris muscle in the right lower limb of an adult male cadaver. Though often dismissed as a small vestigial muscle, an injury to this muscle should actually be included in the differential diagnosis of the painful calf. Also the knowledge of both normal and abnormal anatomy of the plantaris muscle is important for surgeons performing tendon transfer operations and clinicians diagnosing muscle tears.