Prevalence and morphology of the tensor vastus intermedius: cadaveric study and literature comparison

The quadriceps femoris is the main extensor of the knee joint, traditionally described as having four heads. Since the 19th century, reports have suggested an additional head between the vastus lateralis and vastus intermedius. In 2016, Grob et al. described this structure in detail, naming it the tensor vastus intermedius (TVI) and proposing a morphological classification. This study aimed to assess the prevalence, morphology, and dimensions of the TVI in cadaveric specimens and compare the results with the literature. Ten lower limbs from five preserved cadavers (four male, one female) were dissected using a standardized protocol. The presence, Grob type, and dimensions of the TVI were recorded with an electronic caliper. A literature review included only cadaveric studies consistent with Grob's classification and containing quantitative data. The TVI was present in all specimens (100%). The most common type was VL (50%), followed by VI (30%) and bicipital (20%). VI and bicipital types occurred only in males; females showed only the VL type. Identical bilateral types were found in 20% of cases (females). The mean belly length was 105.99 mm, and width was 19.15 mm. Literature reports prevalence ranging from 34% to 100% with variable type distribution. The TVI was a consistent anatomical feature in this sample, with type VL predominating and notable sex-related differences. Findings confirm considerable morphological variability, highlighting potential relevance in imaging interpretation, surgical planning, and rehabilitation. Further imaging-based studies on larger populations are needed to clarify its biomechanical and clinical roles.