| Vastus medialis | |
|---|---|
| Vastus medialis | |
| Muscles of lower extremity | |
| Gray's | subject #128 471 |
| Origin | Medial side of femur |
| Insertion | Quadriceps tendon |
| Artery | femoral artery |
| Nerve | femoral nerve |
| Actions | extends leg |
| Dorlands /Elsevier |
Vastus medialis muscle |
The vastus medialis (aka vastus internus), often called the 'teardrop' muscle, is a medially located muscle of the quadriceps.
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The Vastus Medialis is one of four muscles which resides in the front of the thigh. The vasti 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. However, this does not apply to persons with trochlear aplasia or hypoplasia, which refer to an absence or extreme shallowness of the trochlear groove.[1] Some authorities maintain there is a separate aspect to the Vastus Medialis muscle - the "Vastus Medialis Obliquus"[2] or more commonly the "VMO"[3] 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 (i.e. gluteus maximus), which causes subsequent unusual internal rotation of the femur. Patello-femoral syndrome can also be caused by an injury, a misaligned patella, or changes underneath the patella. The primary symptom of this syndrome is typically knee pain when squatting, sitting, jumping, and ascending and descending stairs. It can also cause the knee to give out suddenly and popping or cracking noises within the knee. One way to relieve the pain is to avoid any activities that require a deep bend in the knee.
Lunges are an exercise sometimes used to target this muscle. Exercises to help strengthen the vastus medialis are the leg press, squat, and leg extension. If there is a patellar tracking problem squats should not be performed and the leg press and extension only the last 20 degrees of extension should be performed.
The Vastus Medialis muscle originates from a continuous line of attachment on the femur, which begins on the front and middle side (anteromedially) on the intertrochanteric line of the femur. It continues down and back (posteroinferiorly) along the pectineal line and then descends along the inner (medial) lip of the linea aspera and onto the medial supracondylar line of the femur. The fibers converge onto the inner (medial) part of the quadriceps femoris tendon and the inner (medial) border of the patella. [4]
"Common Muscular Weaknesses." ExRx (Exercise Prescription) on the Net. Web. 08 Dec. 2009.
<http://www.exrx.net/Kinesiology/Weaknesses.html>.
"Patellofemoral Pain Syndrome-Topic Overview." WebMD - Better information. Better health. Web. 09 Dec. 2009. <http://www.webmd.com/a-to-z-guides/patellofemoral-pain-syndrome-topic-overview>.
This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.
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