Anatomical variations of the plantaris muscle and a potential role in patellofemoral pain syndrome

The plantaris muscle has been given little attention in the reviewed literature. It is most commonly mentioned only when absent from a specimen. This study aimed to document the anatomy of the plantaris muscle and to discuss the clinical significance of the observations. Cadaveric knees (n = 46) were dissected to identify the possible variations of the plantaris muscle. The muscle conformed with standard descriptions (n = 26; 56.52%), was present but varied from previous descriptions (n = 14; 30.44%), or was absent (n = 6; 13.04%). The variations consisted of distinct interdigitations with the lateral head of the gastrocnemius muscle (n = 9; 19.57%) and a strong fibrous extension of the plantaris muscle to the patella (n = 5; 10.87%). The presence of interdigitations strengthen the argument that the plantaris muscle supplement the activity of the lateral head of the gastrocnemius muscle whereas the patellar extension suggests an involvement with patellofemoral dynamics and may play a role in the various presentations of patellofemoral pain syndrome. Greater understanding of the relationship between these and other posterior knee structures will facilitate more precise interpretation and treatment of knee injuries.