Proximal origin variants of the plantaris muscle: a classification-based review with surgical and radiologic implications.

BACKGROUND: The plantaris muscle (PM) is a highly variable structure whose proximal origin demonstrates significant morphological diversity. While traditionally considered clinically insignificant, recent evidence highlights its role in sports injuries, Achilles tendinopathy, and even vascular entrapment syndromes. A structured classification-based approach is therefore essential to improve diagnostic accuracy and surgical safety. METHODS: A classification-focused narrative review of anatomical, radiological and clinical literature was performed using PubMed and Web of Science, supplemented by manual screening of reference lists. Nineteen key articles were synthesised qualitatively, and morphometric frequencies were taken from the original cadaveric classification study of 128 lower limbs. RESULTS: Eight distinct PM configurations were synthesised into a clinically oriented framework: six primary origin types (I–VI) and two special Type VI variants (double and bifurcated plantaris). Type II and the double PM variant have been reported most frequently in association with “tennis leg” and recurrent calf pain, whereas Type IV and bifurcated variants have been implicated in popliteal artery entrapment, mainly in case-based reports. Radiologically, PM variants may mimic neoplastic or cystic lesions, underscoring the need for classification-based interpretation to avoid misdiagnosis. Tables and an algorithmic workflow are presented to guide surgeons and radiologists through variant recognition and risk mitigation. CONCLUSIONS: Not all plantaris muscles are equal. Their anatomical variability directly influences orthopaedic, vascular, and radiological practice. Preoperative identification using MRI or ultrasound, combined with classification-based risk assessment, is critical to minimizing iatrogenic complications and improving patient outcomes. The Olewnik Classification provides a clinically applicable framework that bridges anatomy, surgery, sports medicine, and imaging.