Clinical Anatomy of the Quadriceps Femoris and Extensor Apparatus of the Knee

Abstract

Most descriptions of the extensor mechanism of the knee do not take into account its complexity and variability. The quadriceps femoris insertion into the patella is said to be through a common tendon with a threelayered arrangement: rectus femoris (RF) most superficially, vastus medialis (VM) and lateralis (VL) in the intermediate layer, and vastus intermedius (VI) most deeply. We dissected 20 limbs from 17 cadavers to provide a more detailed description of the anterior components of the knee: the tendon, the patellar retinacula, and the patellofemoral ligaments. Only three of the 20 specimens exhibited the typically described quadriceps pattern. The remainder had bilaminar and even more complex trilaminar and tetralaminar fiber arrangements. We found an oblique head of the vastus lateralis (VLO), separated from the longitudinal head by a layer of fat or fascia, in 60% of the specimens. However, we found no distinct oblique head of the vastus medialis (VMO) in any specimen. The medial patellofemoral ligament (MPFL) was more common than the lateral (LPFL), supporting its suggested role as the principal passive medial stabilizer of the patella. Because the quadriceps muscle group plays a direct role in patellofemoral joint function, investigation into the clinical applications of its highly variable anatomy may be worthwhile with respect to joint dysfunction and failures of TKAs.

Atualização da anatomia do mecanismo extensor do joelho com uso de técnica de visualização tridimensional

“…Despite several classical anatomical studies on cadavers, doubts persist regarding the presence, location, anatomical variations and function of some structures in the joint dynamics of the knee extensor mechanism (2,(4)(5)(6) .…”

“…A recent study demonstrated that this classical trilaminar description is in reality a complex structure with large anatomical variation and poorly defined fascial planes (2) .…”

“…The insertions are located in the medial epicondyle and in the proximal 2/3 of the medial face of the patella (1,2,5) . Other secondary medial stabilizers of the patella that have been described include the medial retinaculum, patellomeniscal ligament and patellotibial ligament (1,5) .…”

“…In addition to these, the mechanism also includes the patellar retinacula, restrictor ligaments, Hoffa's fat pad and the pre-patellar tissue (1,2) .…”

Sonography of the quadriceps muscle: Examination technique, normal anatomy, and traumatic lesions

“…A fairly small portion of the fibers of the superficial lamina lies superficial to the patella and merge directly into the patellar tendon. The description supplied above corresponds to that provided by most anatomy textbooks, but recent studies based on anatomical dissections, have revealed considerable variability in the composition of the distal tendon [7].…”