| Vastus medialis | |
|---|---|
 Muscles of lower extremity (Rectus Femoris has been removed) | |
| Details | |
| Origin | Medial side of femur |
| Insertion | Quadriceps tendon |
| Artery | Femoral artery |
| Nerve | Femoral nerve |
| Actions | Extendsknee |
| Identifiers | |
| Latin | musculus vastus medialis or musculus vastus internus |
| TA98 | A04.7.02.023 |
| TA2 | 2620 |
| FMA | 22432 |
| Anatomical terms of muscle | |
Thevastus medialis (vastus internus orteardrop muscle) is anextensormuscle locatedmedially in thethigh that extends theknee. The vastus medialis is part of thequadriceps muscle group.
The vastus medialis is a muscle present in theanterior compartment of thigh, and is one of the fourmuscles that make up thequadriceps muscle. The others are thevastus lateralis,vastus intermedius andrectus femoris.[1] It is the most medial of the "vastus" group of muscles. The vastus medialis arises medially along the entire length of thefemur, and attaches with the other muscles of the quadriceps in thequadriceps tendon.[1]
The vastus medialis muscle originates from a continuous line of attachment on the femur, which begins on the front and middle side (anteromedially) on theintertrochanteric line of the femur. It continues down and back (posteroinferiorly) along thepectineal line and then descends along the inner (medial) lip of thelinea aspera and onto the medial supracondylar line of the femur. The fibers converge onto the inner (medial) part of the quadriceps tendon and the inner (medial) border of thepatella.[1]
Theobliquus genus muscle is the most distal segment of the vastus medialis muscle. Its specific training plays an important role in maintaining patella position and limiting injuries to the knee. With no clear delineation, it is simply the most distal group of fibers of the vastus medialis.
The vastus medialis is one of four muscles in theanterior compartment of the thigh.[1] It is involved in knee extension, along with the other muscles which make up thequadriceps muscle.[1] The vastus medialis also contributes to correct tracking of the patella.[2]
A division of the vastus medialis muscle into two groups of fibers has been hypothesized, a long and relatively inline group of fibres with the quadriceps ligament, thevastus medialis longus; and a shorter and more obliquely oriented with group of fibres, thevastus medialis obliquus. There is as yet insufficient evidence to conclusively confirm or deny this hypothesis.[3]
Knee pain is thought to be primarily associated with specific quadriceps muscle weakness orfatigue, especially in the vastus medialis obliquus (VMO). It is known that fatigue can be caused by many different mechanisms, ranging from the accumulation ofmetabolites within muscle fibers to the generation of an inadequate motor command in themotor cortex.[4] Characteristics of the vastus medialis, including its angle of insertion, correlate with presence ofknee joint pain (patellofemoral pain syndrome).[5] However, this syndrome is complex and definitive evidence of causality has not yet been published.
Misfiring and fatiguing of the VMO causes mal-tracking of the patella and subsequent damage to surrounding structures creating increased force on the knees, often resulting in injuries such aspatellofemoral pain syndrome,anterior cruciate ligament rupture,chondromalacia, andtendinitis.[6] Through the use ofelectromyography, researchers can evaluate and record the electrical activity produced by the skeletal muscle of the VMO to analyze thebiomechanics and detect any possible abnormalities, weakness, or fatigue. With an analysis of muscle activity of the VMO through the use of electromyography, proper rehabilitative plans and goals can be established to not only correct the already established abnormality, but even prevent such injuries if tested sooner. Preventing injuries is crucial as well as teaching proper training techniques to ensure there are no valgus collapse forces causing unplanned stress on other structures of the knee, causingasymmetry, and predisposing that individual for injury.
This article incorporates text in thepublic domain frompage 471 of the 20th edition ofGray's Anatomy(1918)
