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

extensor In anatomy, extension is a movement of a joint that increases the angle between two bones or body surfaces at a joint. Extension usually results in straightening of the bones or body surfaces involved. For example, extension is produced by extendin ...

muscle 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. 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 muscles that make up the

quadriceps The quadriceps femoris muscle (, also called the quadriceps extensor, quadriceps or quads) is a large muscle group that includes the four prevailing muscles on the front of the thigh. It is the sole extensor muscle of the knee, forming a large ...

muscle. The others are the

vastus lateralis The vastus lateralis (), also called the vastus externus, is the largest and most powerful part of the quadriceps femoris, a muscle in the thigh. Together with other muscles of the quadriceps group, it serves to extend the knee joint, moving the ...

vastus intermedius The vastus intermedius () (Cruraeus) arises from the front and lateral surfaces of the body of the femur in its upper two-thirds, sitting under the rectus femoris muscle and from the lower part of the lateral intermuscular septum. Its fibers en ...

and

rectus femoris The rectus femoris muscle is one of the four quadriceps muscles of the human body. The others are the vastus medialis, the vastus intermedius (deep to the rectus femoris), and the vastus lateralis. All four parts of the quadriceps muscle attach ...

. 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 wit ...

, and attaches with the other muscles of the quadriceps in the

quadriceps tendon In human anatomy, the quadriceps tendon works with the quadriceps muscle to extend the leg. All four parts of the quadriceps muscle attach to the shin via the patella (knee cap), where the quadriceps tendon becomes the patellar ligament. It att ...

. 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 The intertrochanteric line (or ''spiral line of the femur''White (2005), p 256 ) is a line located on the anterior side of the proximal end of the femur. Structure The rough, variable ridge stretches between the lesser trochanter and the greater ...

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 The linea aspera ( la, rough line) is a ridge of roughened surface on the posterior surface of the shaft of the femur. It is the site of attachments of muscles and the intermuscular septum. Its margins diverge above and below. 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

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, 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 In biochemistry, a metabolite is an intermediate or end product of metabolism. The term is usually used for small molecules. Metabolites have various functions, including fuel, structure, signaling, stimulatory and inhibitory effects on enzymes, ...

within muscle fibers to the generation of an inadequate motor command in the

motor cortex The motor cortex is the region of the cerebral cortex believed to be involved in the planning, control, and execution of voluntary movements. The motor cortex is an area of the frontal lobe located in the posterior precentral gyrus immediately ...

. Characteristics of the vastus medialis, including its angle of insertion, correlate with presence of knee 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 sitti ...

). 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 ligament Cruciate ligaments (also cruciform ligaments) are pairs of ligaments arranged like a letter X. They occur in several joints of the body, such as the knee joint and th ...

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 in ...

, and

tendinitis Tendinopathy, a type of tendon disorder that results in pain, swelling, and impaired function. The pain is typically worse with movement. It most commonly occurs around the shoulder (rotator cuff tendinitis, biceps tendinitis), elbow (tennis elbo ...

. Through the use of electromyography, researchers can evaluate and record the electrical activity produced by the skeletal muscle of the VMO to analyze the

biomechanics Biomechanics is the study of the structure, function and motion of the mechanical aspects of biological systems, at any level from whole organisms to organs, cells and cell organelles, using the methods of mechanics. Biomechanics is a branch of ...

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, 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