Beyond four heads: Should the quadriceps femoris be reclassified as multiceps muscle?

The quadriceps femoris (QF) is classically described as a four-headed muscle. However, anatomical and radiological studies increasingly reveal supernumerary heads and tendon stratifications, challenging this concept.

This review synthesizes current cadaveric, imaging, and surgical evidence to propose a reclassification of QF as a multiceps femoris (MF). A five-type tendon-based classification system is introduced, reflecting distinct morphological variants and layering complexities.

An extensive review of anatomical dissection studies, radiological investigations (MRI and ultrasound), and clinical reports were conducted to evaluate morphological variability and its implications for tendon harvesting and surgical access.

Accessory heads such as the tensor vastus intermedius and caput tertium were present in over 60 % of cases, often contributing to distinct layers within the quadriceps femoris tendon (QFT). These configurations influence graft length, harvesting safety, and radiological interpretation. Misidentification of these structures may result in surgical complications or diagnostic errors. Functional and evolutionary analogies with other multiceps systems support the anatomical independence of these heads.

The MF model aligns with modular systems seen in the triceps surae and biceps femoris. Recognizing QF as MF offers a more anatomically accurate and clinically relevant framework. Adoption of updated terminology and imaging protocols may improve diagnosis, reduce surgical risk, and support personalized interventions.