Morphological classification of the plantaris muscle origin: a cadaveric study

The plantaris muscle (PM), considered vestigial in humans, has clinical significance owing to its anatomical variations. This study examined the prevalence, origin types, and clinical relevance of the PM in the Korean population to aid clinical and surgical practices, particularly in posterior knee surgery. A total of 160 lower limbs (90 male, 70 female) were dissected using classical anatomical methods. The morphology of PM origin was classified, and its prevalence was evaluated. The PM was present in 146 lower limbs (91.25%). Three distinct origin types were observed: Type 1 (68.18%), originating from the knee joint capsule, the lateral condyle of the femur (LFC), and the lateral head of the gastrocnemius muscle (lhGM), with fibers blending into the lhGM tendon; Type 2 (17.53%), originating from the knee joint capsule and the LFC but not blending with the lhGM tendon; and Type 3 (5.19%), originating solely from the LFC and the knee joint capsule, without any attachment to or connection with the lhGM. The average PM muscle belly length and width were 9.56 ± 1.71 cm, and 1.80 ± 0.64 cm, respectively. The PM shows morphological variability according to its origin attachment types. These findings provide valuable baseline data for understanding the anatomy of the PM, which can assist surgeons in diagnosing and treating conditions associated with posterior knee pain.