The vastus medialis (vastus internus or teardrop muscle) is an extensor

muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of mus ...

located medially in the

thigh In human anatomy, the thigh is the area between the hip ( pelvis) and the knee. Anatomically, it is part of the lower limb. The single bone in the thigh is called the femur. This bone is very thick and strong (due to the high proportion of ...

that extends the

knee In humans and other primates, the knee joins the thigh with the leg and consists of two joints: one between the femur and tibia (tibiofemoral joint), and one between the femur and patella (patellofemoral joint). It is the largest joint in the ...

. The vastus medialis is part of the quadriceps muscle group.

Structure

The vastus medialis is a muscle present in the anterior compartment of thigh, and is one of the four

s that make up the quadriceps muscle. The others are the vastus lateralis, vastus intermedius and rectus femoris. It is the most medial of the "vastus" group of muscles. The vastus medialis arises medially along the entire length of the

femur The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates ...

, and attaches with the other muscles of the quadriceps in the quadriceps tendon. 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 tendon and the inner (medial) border of the

patella The patella, also known as the kneecap, is a flat, rounded triangular bone which articulates with the femur (thigh bone) and covers and protects the anterior articular surface of the knee joint. The patella is found in many tetrapods, such as ...

. The obliquus 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.

Function

The vastus medialis is one of four muscles in the anterior compartment of the thigh. It is involved in knee extension, along with the other muscles which make up the quadriceps muscle. The vastus medialis also contributes to correct tracking of the patella. 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, the ''vastus medialis longus''; and a shorter and more obliquely oriented with group of fibres, the ''vastus medialis obliquus''. There is as yet insufficient evidence to conclusively confirm or deny this hypothesis.

Clinical significance

Knee pain

Knee pain is thought to be primarily associated with specific quadriceps muscle weakness or

fatigue Fatigue describes a state of tiredness that does not resolve with rest or sleep. In general usage, fatigue is synonymous with extreme tiredness or exhaustion that normally follows prolonged physical or mental activity. When it does not resolve ...

, especially in the vastus medialis obliquus (VMO). It is known that fatigue can be caused by many different mechanisms, ranging from the accumulation of metabolites within muscle fibers to the generation of an inadequate motor command in the motor cortex. Characteristics of the vastus medialis, including its angle of insertion, correlate with presence of

joint pain (

patellofemoral pain syndrome Patellofemoral pain syndrome (PFPS; not to be confused with jumper's knee) is knee pain as a result of problems between the kneecap and the femur. The pain is generally in the front of the knee and comes on gradually. Pain may worsen with sittin ...

). 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 as

anterior cruciate ligament The anterior cruciate ligament (ACL) is one of a pair of cruciate ligaments (the other being the posterior cruciate ligament) in the human knee. The two ligaments are also called "cruciform" ligaments, as they are arranged in a crossed formati ...

rupture,

chondromalacia Chondromalacia patellae (also known as CMP) is an inflammation of the underside of the patella and softening of the cartilage. The cartilage under the kneecap is a natural shock absorber, and overuse, injury, and many other factors can cause inc ...

, and tendinitis. Through the use of

electromyography Electromyography (EMG) is a technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG is performed using an instrument called an electromyograph to produce a record called an electromyogram. An electromyo ...

, researchers can evaluate and record the electrical activity produced by the skeletal muscle of the VMO to analyze the biomechanics 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, causing

asymmetry Asymmetry is the absence of, or a violation of, symmetry (the property of an object being invariant to a transformation, such as reflection). Symmetry is an important property of both physical and abstract systems and it may be displayed in pre ...

, and predisposing that individual for injury.

Additional images

File:Gray245.png, Right femur. Posterior surface. File:Vastus medialis muscle.png, Muscles of the iliac and anterior femoral regions. File:Gray550.png, The femoral artery. File:Anatomical dissection2.JPG, Vastus medialis File:Slide8rrr.JPG, Vastus medialis muscle File:Slide6www.JPG, Vastus medialis muscle File:Slide5CCCC.JPG, Vastus medialis muscle File:Slide5FFFFF.JPG, Vastus medialis muscle File:Slide10WWWW.JPG, Vastus medialis muscle File:Slide2EA.JPG, Muscles of thigh. Cross section.

References

External links

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PTCentral
{{DEFAULTSORT:Vastus Medialis Knee extensors Muscles of the quadriceps Anterior compartment of thigh Muscles of the lower limb