Vastus medialis

Vastus medialis
Vastus medialis
Muscles of lower extremity
Gray's	subject #128 471
Origin	femur
Insertion	patella
Artery	femoral artery
Nerve	femoral nerve
Actions	extends leg
Dorlands /Elsevier	Vastus medialis muscle

The vastus medialis, often called the 'teardrop' muscle, is a medially located muscle of the quadriceps.

Function

The vasti instead appear to act largely in a co-ordinated manner throughout the control of knee extension. Much has been made of the ability of the Vastus Medialis to translate the patella medially, however since approximately 70% of the contractile fibres attach directly to the common extensor tendon (which then inserts centrally to the superior patella) the functional ability to achieve this goal may be overstated, and is likely dwarfed by the bony congruence of the patella in the trochlea notch. Some authorities maintain there is a separate aspect to the Vastus Medialis muscle - the "Vastus Medialis Obliquus"^[1] or more commonly the "VMO"^[2] which is reported to have a more oblique or horizontal orientation to the bulk of the remainder of the muscle thereby disposing it to be better able to 'pull' the patella medially. Unfortunately careful inspection of many cadavers reveals that the fibres of the Vastus Medialis are largely parallel and there is no significant separate aspect of the contractile fibres fitting this description which would suggest it is time to lay this clinical myth to rest.

Often medical and other allied health practitioners suggest improving the strength and/or activation of this muscle as a strategy in the treatment of Patello-femoral Pain Syndrome - sometimes called runner's knee. The biomechanical cause of patellofemoral pain syndrome is unknown and may have more to do with weakness of extensors of the hip (ie gluteus maximus), which causes subsequent unusual internal rotation of the femur.

Lunges are an exercise sometimes used to target this muscle.

Origin and insertion

The vastus medialis arises by an aponeurosis, which is attached to the lower part of the line that extends from the inner side of the neck of the femur to the linea aspera, from the whole length of the linea aspera, and the internal intermuscular septum. It also arises from nearly the whole of the internal, anterior and external surfaces of the shaft of the femur, limited above by the line between the two trochanter and extending below to within the lower fourth of the bone.

The fibres converge to a broad aponeurosis, which covers the anterior surface of the middle portion of the cruraeus and the deep surface of the inner division of the present muscle becoming joined and gradually narrowing; it is inserted into the patella, blending with the other portions of the quadriceps extensor.

Relations

The Vastus medialis and Vastus intermedius appear to be inseparably united, but when the Rectus femoris has been reflected a narrow interval will be observed extending upward from the medial border of the patella between the two muscles, and the separation may be continued as far as the lower part of the intertrochanteric line, where, however, the two muscles are frequently continuous.

Additional images

Right femur. Posterior surface.

Muscles of the iliac and anterior femoral regions.

The femoral artery.

References

External links

• The KNEEguru - educational site packed with knee content with sections on the quadriceps muscle
• LUC vasm
• Cross section at UV pembody/body18b
• Vastus+medialis+muscle at eMedicine Dictionary
• PTCentral

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated.