Prevalence and anatomical characteristics of the tensor vastus intermedius: a systematic review and meta-analysis

Abstract

The tensor vastus intermedius (TVI) has recently been proposed as a distinct fifth head of the quadriceps femoris (QF). However, reported prevalence rates vary significantly. This systematic review and meta-analysis aimed to estimate the pooled prevalence of the TVI and examine its morphological characteristics and potential sources of heterogeneity. A comprehensive search of PubMed, Scopus, Web of Science, and Google Scholar was conducted through March 2026. Inclusion criteria targeted original human studies (cadaveric or radiologic) reporting TVI prevalence. A random-effects model was used to estimate the pooled prevalence of the TVI, accounting for clinical and methodological heterogeneity. To address extreme prevalence values (0% or 100%), the Freeman–Tukey double arcsine transformation was applied to stabilize variances and ensure appropriate weighting of all studies. Seventeen articles yielding 19 independent datasets encompassing 865 lower limbs were included. The pooled prevalence of the TVI was 83% (95% CI: 67–95%). Substantial heterogeneity was observed (I 2 = 96.2%). Subgroup analyses revealed no significant differences based on study type, sex, or laterality. Sensitivity analysis excluding studies with 100% prevalence reduced the estimate to 47%. Evidence of publication bias was detected, with smaller studies reporting higher prevalence. The TVI appears to be a frequently reported anatomical variant within the QF complex; however, the pooled prevalence estimate should be interpreted cautiously because of substantial heterogeneity and small-study effects. Awareness of the TVI may be relevant during knee surgery and radiological assessment and may contribute to a better understanding of extensor mechanism anatomy.