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You are watching: Muscles that act on the knee joint form most of the mass of the __________.

StatPearls . Endowment Island (FL): StatPearls Publishing; 2021 Jan-.


Anatomy, Bony Pelvis and Lower Limb, Thigh Quadriceps Muscle

Bruno Bordoni; Matthew Varacallo.

Author Information


The quadriceps femoris is the many voluminous muscle the the person body.

From a sporting point of view, the is one extraordinarily necessary muscle, but due to the stress it receives, that is frequently subject come trauma. The quadriceps is vital for daily activities, such together climbing stairs or obtaining up indigenous the chair. Quadriceps can become a diagnostic device in part pathological conditions, studying the intrinsic adaptations of muscle tissue. Part flaps of muscle tissue deserve to be used to repair components of the skull or various other contractile districts.

Recent information on the duty and anatomy of this muscle will improve the expertise of the practical coordination in between the different vasti and permit implementation of a clinical and rehabilitative approach. That functions influence the knee joint, hip joint, posture, walking, and also the relationship between the pelvis and also the spine.

Structure and also Function

The action of the quadriceps femoris have consequences on the knee and also hip joints. The rectus femoris can flex the hip, if its synergistic action with vastus lateralis, vastus medialis, and vastus intermedius extend the knee.

The myoelectric balance that the quadriceps is essential for a correct movement of the patella.

The proprioceptive afferents that the muscle contribute to keeping adequate posture. Current studies display that the activation of these afferents allows the contralateral quadriceps muscle to boost its coordination, increasing postural balance. The quadriceps allows an independent walk, helps with stair climbing, and enables one to lift indigenous a chair.

The rectus femoris can activate its yarn in the longitudinal mode. It have the right to activate the proximal yarn in the absence of convulsion of the most distal fibers. If the action of the quadriceps continues, it will certainly activate the many distal fibers, in the lack of the most proximal ones. That is more than likely a system to hold-up the onset of fatigue.

The patellar tendon insertion that the vastus medialis is small and is no able to create a force capable of medially stability the patella throughout knee extension. The pressure expressed by the vastus medialis during the extension is modest. In reality, during its contraction, it traction the aponeurosis the the vastus intermedius, counteracting the lateral pressures on the patella of the vastus lateralis. The vastus medialis action indirectly together a patellar stabilizer, place its contractile force on the mean axis the the femur.

The toughness expressed through the vastus lateralis boosts with the rise in knee flexion. This device is due to the size of the fibers compared to the connective structure of the muscle. Much longer fibers express better strength and make far better use that the elasticity or resistance the the connective tissue. Once the knee is extended, the vastus lateralis areas a small force the is useful for preserving the place with minimal effort.

The adhering to are the functions of the quadriceps muscle:

It is composed of the rectus femoris (RS) that originates from the anterior inferior iliac spine with the direct tendon, and also the upper rim of the acetabulum through the indirect tendon. With a 3rd and small tendon (reflected tendon), it attaches come the hip joint capsule anteriorly. The very first 2 RS tendons continue downward with two aponeurotic laminae, approximately two-thirds of the rectus femoris. The straight tendon will come to be the superficial lamina when the indirect tendon continues as a central sagittal lamina.
The vastus lateralis (VL) that originates from the lateral face of the good trochanter, indigenous the gluteal tuberosity and also the lateral lip of the linea aspera.
The vastus medialis (VM) that takes an attack from the anatomical neck of the femur and also the medial lip that the linea aspera. The vastus medialis is deeply put in the aponeurosis that the vastus intermedius, if the tensor of the vastus intermedius is put in the very same aponeurosis, more superficial.
The vastus intermedius (VI) originates native the proximal three-fourths that the anterior and lateral deals with of the femoral body, and also from the lateral lip the the linea aspera. Some bundles that the vastus intermedius are inserted in the top recess of the supra-patellar bursae, making up the articular muscle that the knee.

The 4 heads room directed bottom to kind a solitary tendon, the quadriceps muscle tendon, which fits top top the patella. The most superficial fibers of the tendon continue and also cover the patella, inserting itself on the tibial tuberosity referred to as the patellar ligament. The connective yarn of the vastus lateralis and vastus medialis attach themselves to the margins of the patella; the connective fibers of the vastus intermedius insert at the base of the patella. Some connective yarn come indigenous the RS, and along with connective yarn of vastus lateralis/vastus medialis, will type the lateral and medial retinacula of the patella.

Recently, one more muscle, the tensor that the vastus intermedius (TVI), has been established as part of the quadriceps femoris. The tensor the the vastus intermedius starts from the anteroinferior portion of the good trochanter. It joins v a broad flat aponeurosis between vastus lateralis and vastus intermedius in the main area the the thigh, and they join with a single tendon in the upper part of the patella, merging into the quadriceps tendon. At the dorsal level of the thigh, the muscle fibers of this 3 muscle merge in the vicinity the the linea aspera the the femur. At the level that the great trochanter, this muscle also can originate from the gluteus minimus.

We do not understand much about its functions; however, it most likely allows, together with the various other districts, a correct activity of the patella and/or put the intermedius muscle in tension.


The body buds departure from the ventrolateral surface ar of the human body wall. The gems contain the mesenchyme the somatopleural, extended by one apical ectodermal crest. The cell of the hypomere (ventral component of the myotome of a somite) migrate from the somite inside the sprout to form the muscle cells. The connective organization of the limbs derives from the mesenchyme the the somatopleural. This happens about the fifth week the gestation. The gems rotate around 90 degrees medially, along with a longitudinal axis. This movement of the knee area will be located in the prior portion.

Blood Supply and Lymphatics

The femoral artery nourishes the quadriceps muscle. It represents the extension of the external iliac artery (behind the inguinal ligament). It descends in the anteromedial part of the thigh come the ring of the adductor channel where it i do not care a popliteal artery. That is feasible to imagine the femoral artery as a directly line connecting the facility of the inguinal canal come the posterior portion of the medial condyle that the femur. Among its most vital branches for the quadriceps muscle, we cite the superficial and also deep femoral artery.

The femoral vein is the extension of the popliteal vein, to arrive, adhering to the course of the femoral artery, approximately the inguinal ligament, and become the exterior iliac vein.

The lymphatic vessels of the lower limb reach the lumbar aortic lymph nodes, i m sorry are part of the right and also left lumbar trunks; drainage will reach the cisterna chyli.


The femoral nerve originates indigenous L2 to L4, innervating the contractile areas of the thigh anteriorly (quadriceps muscle, sartorius muscle), of the i know good (comb) and the skin in the anteromedial section of the thigh, knee, leg, and the earlier of the foot. It additionally contains yarn from L1. The roots converge downward and also sideways in the thickness that the big psoas muscle, involvement in a solitary trunk close to the transverse process of L5. The developed nerve descends and also exits caudally from the outer portion of the psoas muscle and continues traveling caudally in the middle of the psoas/iliac muscle complex. In this area, it is spanned by the iliac fascia which separates it from the parietal peritoneum, the cecum colon top top the right and also the sigmoid colon on the left.

The fascial device that constitutes the nerve problems not only the organization it the cross from the electrical suggest of see but additionally from the mechanical point of view. This is because a palliation in that elasticity will decrease the capability of the joints that are associated by its i to move. As soon as an entrapment syndrome is recorded, the nerve acts prefer a fascial brake.

Arriving at the inguinal ligament, the femoral nerve adheres to the iliopsoas musculature and divides right into some ramifications at about 2 centimeters past the inguinal ligament, medial to the sartorius muscle and lateral to the femoral artery. The nerve in this area is broader and flattened; in part subjects, the nerve can come to be arborized before it overcome the inguinal ligament. At this level, the femoral nerve gives small superficial ramifications to the skin and also the fascial structures.

Before branching, the femoral nerve enters (having happen the inguinal ligament) right into the femoral lacuna (consisting that the femoral nerve and also the iliopsoas muscle complex).

It continues in the Scarpa triangle or femoral triangle (pyramidal fossa v the caudal oriented apex found in the anterosuperior and also medial area that the thigh, whereby the apex is formed by the adductor and also sartorius muscle, the lateral section consists the the sartorius muscle, and also the medial one from the long adductor). Right here there space vessels and lymphatic pathways (the Cloquet lymph node).

The effects of the femoral nerve are uncovered for the most part in the Scarpa triangle, whereby we find the medial sartorius nerve, the pectineus nerve, the medial and lateral musculocutaneous nerve, the femoral nerve command to the quadriceps muscle branches by the miscellaneous vasti muscles, and the saphenous nerve.

The femoral nerve directed to the vastus lateralis is divided into 2 branches, which will certainly divide right into 2 other branches each through a course from anteriorly and also proximally come posteriorly and distally.

The femoral nerve innervating the vastus medialis complies with the anteromedial border the the muscular district. The vastus intermedius receives innervation indigenous the femoral nerve, which arrives in the medial section of the vastus. The tensor that the vastus intermedius is innervated starting from its proximal portion. The rectus femoris receive innervation near the anterior inferior iliac spine.


The femoral quadriceps muscle has more superficial anaerobic fibers while going to the depth, and also there will certainly be more aerobic fibers. The an initial fibers are much less vascularized than the oxidative fibers; the white fibers will certainly be activated after the activation that the red fibers. During a contraction, there will be slower deoxygenation of the depth fibers.

Men express a better percentage that contractile strength and also speed than women, probably due to the fact that men have greater muscle mass because that men and also hormone levels. Testosterone facilitates the rate of the motor unit"s electric impulse, disclosure a higher amount and also speed that calcium relax within the fibers (faster contraction), and also stimulates a faster repair procedure and a larger hypertrophic response. In men, the percentage of white fibers is higher.

Physiologic Variants

The Tensor of the Vastus Intermedius

The tensor the the vastus intermedius have the right to be classified into 4 morphological types, based on the place of the aponeurosis.

The an initial type or independent kind originates from the upper portion of the intertrochanteric line and the anterior section of the an excellent trochanter. Its beginning is separated indigenous the origin of the vastus intermedius in around 33% the the population. The fascia or aponeurosis continues to be separated indigenous the vastus lateralis and the vastus intermedius.
In the second type it originates in addition to the vastus intermedius; the aponeurosis is separable native the vastus lateralis. This morphology involves about 8% of the population.
In the 3rd type, the muscle originates native the vastus lateralis, while the aponeurosis is separable from the vastus intermedius. The portion is around 30%.
The typology of kind four or usual typology, originates from the vastus lateralis, with the aponeurosis separable from the lateral vastus and also the vastus intermedius. The recognize is around 27%.

Vastus Medialis

According to some authors, the vastus medialis can be separated into vastus medialis obliquus and also vastus medialis longus, based on the orientation that the fibers. The an initial portion is much more innervated 보다 the second portion.

Vastus Lateralis

In the literature are not reported important changes in the vastus lateralis. That origin and also insertion stay constant, as researches on cadavers confirm.

Vastus Intermedius

This section of the quadriceps muscle may exhibit sport in that is insertions or origin. That may present with a smaller area that the femur or broader attachment; it have the right to involve the vastus lateralis in that origin, creating a single origin that the 2 vasti.

Rectus Femoris

The rectus femoris may have actually accessory muscles. A muscle slip could result from the acetabulum and also fit straight into the vastus lateralis. Two unique muscular districts might constitute the rectus femoris. The origin might vary native deriving from the upper anterior iliac spine come deriving only from the reduced anterior iliac spine in the lack of the acetabular origin. The vastus can fit directly into the vastus intermedius.

Surgical Considerations

Quadriceps Tendon Ruptures<1><2>

Distal quadriceps tendon ruptures most frequently occur in patients end 40 year of age. Distal quadriceps tendon ruptures most frequently occur at its insertion allude at the premium pole of the patella and also have an incidence rate greater than that of its patellar tendon rupture counterpart.

Unless medical comorbidities preclude the overwhelming benefits and also positive outcomes from main repair, surgical intervention is recommended. Indications for nonoperative management are minimal to partial tears when the patience still has an intact extensor mechanism. In the last situation, the patient deserve to be inserted in a knee immobilizer or a hinged knee brace locked in expansion for 2 come 3 weeks depending on the degree of partial injury. ~ repeat clinical evaluation, the patient is instantly prescribed a rigorous physical treatment regimen to combat imminent knee stiffness and also quadriceps atrophy. Until the patient can show adequate quadriceps muscle control, the knee brace is to be worn during ambulation. When the quadriceps demonstrate post-rehabilitation strength that is comparable come the contralateral extremity, the brace serves an assisting role in augmenting the dynamic stability of the knee joint itself. Any type of injuries affecting muscles, tendons, or ligaments cross the knee joint (in this case, the quadriceps functionally crosses the knee joint via the extensor mechanism and also patellar tendon) must be treated following the same rehabilitation clinical pearls and parameters.

The very same rehabilitation parameters mentioned above are accurate in the postoperative duration following major repair. Automatically following the repair, patient are retained in a brace locked in expansion for around 2 mainly and allowed to load bear together tolerated (WBAT) v bilateral crutch assistance. Physical treatment starts at this time in the postoperative period, using quad stimulation modalities to assist mitigate an extensive atrophy. The therapist additionally should be functioning on aggressive patellar mobilization in all directions. Patellar mobility is imperative as this dram a an essential role in preventing knee stiffness.  maintaining the really patella itself mobile as the knee remains restricted secondary come pain and also immobility during the whole recovery period is crucial in offering the patience the ideal chance of afford the finest possible outcome. Early on passive range of activity (ROM) is perform by the therapist, focusing on getting the knee "straight" to terminal extension, and progressively increasing flexion goals from week come week (as identified by the surgeon). No energetic knee extension is permitted at the very least for the first 4 mainly to safeguard the operation repair as the tendon is enabled to heal. Active flexion is again identified by the surgeon and also starts at an early stage on in the rehab process.

While individual therapy protocol will certainly vary based upon the operating surgeon, most begin more aggressive increases in active and active-assist knee flexion goals by mainly 5 as soon as they may institute energetic knee extension exercises. Aquatic therapy often allows for early energetic knee expansion protocols. By 6 weeks, most surgeons aim for unlocking the knee brace increasingly with ambulation. This usually begins by weeks 5 or 6, with the score of hopefully achieving ROM 0 to 120 by weeks 6 come 8 postoperatively. A 2008 examine outlined ROM goal parameters come 50 consecutive patients v either quad or patellar tendon rupture repairs. Both teams of patient hit the 0 to 120 degree ROM mark between 7 and 8 weeks postoperatively. By 12 weeks, all 50 patients accomplished knee flexion same to or in ~ 10 degrees of the contralateral normal knee.  by 6 months, 80% of patients demonstrated no evidence of any type of residual extensor lag.<2>

Setting patience expectations v respect to the recovery procedure is important. According to literature, recovery is very slow and unsatisfactory for the patient, regardless of the operation approach. One of the causes is the ache that might persist and the visibility of scar tissue and also adherence to the tendinous tissue. This leader to an inability to completely use the quadriceps muscle and also the partial ns of proprioceptive information valuable to the muscle. Patients reporting an unsatisfactory outcome is overwhelmingly second to an extensor lag and also knee stiffness that compromises the ability to either return to sport (at prior competition level) or return to baseline recreational activity and/or ADLs.

Other operation Considerations

Surgical viewpoints in complete Knee Arthroplasty (TKA)<3>

The most typical approaches for the standard major TKA procedure encompass the medial parapatellar, midvastus, and subvastus approaches.  when each strategy has theoretical advantages and disadvantages, overall the literature remains controversial concerning the best as whole surgical technique for TKA.

The medial parapatellar method is commonly utilized and entails proximal dissection with a medial cuff of the quadriceps tendon come facilitate exceptional tissue quality closure at the conclusion of the procedure. Distally, a meticulous, continuous medial subperiosteal dissection sleeve is performed if maintaining intimacy with the proximal tibial bone. The degree of dissection is frequently dictated by the anticipated quantity of deformity to be corrected. In general, this medial relax is wild in situations of serious varus deformity, and also most minimal in instances of center to progressed valgus knee deformity. The medial meniscus is also resected v this sleeve of soft tissue.

Alternatives to the conventional medial parapatellar arthrotomy include the midvastus and subvastus approaches. The midvastus approach spares the quadriceps tendon. Instead, the vastus medialis obliquus (VMO) muscle ship is dissected follow me a trajectory directed towards the superomedial facet of the proximal pole of the patella.

The subvastus approach also spares the quadriceps tendon and lifts the muscle belly of the VMO off the intermuscular septum. The subvastus approach preservation the vascularity the the patella and also is cautioned together it can limit exposure in particularly challenging cases or particularly obese patients.

Quadriceps muscle During complete Hip Arthroplasty (THA)

Postoperatively complying with THA, the bulk of patients report a satisfactory outcome.<4> With respect to quad considerations, beforehand rehabilitation and also progressive ambulation (including gait re-training protocols) room imperative to strengthen all of the muscles of the reduced extremity. Surgically, the anterior thigh is given details attention throughout the straight anterior method for THA.

The DA method is becoming increasingly popular amongst THA surgeons. The internervous expression is in between the tensor fascia lata (TFL) and also sartorius on the superficial end, and also the gluteus medius and rectus femoris (RF) top top the deep side. DA THA advocates point out the theoretical diminished hip dislocation prices in the postoperative period and the avoidance of the hip kidnapping musculature.

The disadvantages incorporate the finding out curve connected with the technique as the literature records the decreased complication prices after a operated doctor surpasses the much more than 100-case mark. Other disadvantages incorporate increased wound complications in particularly obese patients with huge panni (without the use of an ab binder), daunting femoral exposure, the threat of lateral femoral cutaneous nerve (LFCN) paresthesias, and also a potentially higher rate of intra-operative femur fractures. Finally, countless surgeons need access to a committed operating table with accordingly trained personnel and also surgical technicians to assist in the procedure. Return the last is not always required, finding out to carry out the procedure on a continual operating table likewise requires a substantial learning curve that have to be considered.<5>

Reconstruction that Quadriceps Muscle

Sarcomas are a type of cancer the may happen in the anterior compartment of the thigh. The surgeon can pick which muscle flap to eliminate from the reduced limb to reconstruct that part of the sectioned quadriceps muscle. The decision will rely not only on the method of the operated doctor but likewise on the size and depth of the tumor. The prognosis of recovery of the quadriceps features is never positive since strength and muscle mass are lost, and persistent pain, scars, and adherence makes the motion of the limb much more disadvantaged. 

Following trauma, the should rebuild part of the muscle might arise. The prognosis will always be negative, through a recovery the will depend on the level of the surgery.

Another reason of quadriceps surgical procedure is the fix of the rectus femoris. The last vastus is well-off in white fibers and also is qualified of developing much force, specifically during an eccentric contraction. In sports where motions are required such as sudden decelerations or slowing under to against an vital load, the possibilities of muscle breakdown, total or parcel, increase. In those cases, wherein the patience requires functional restoration, restoration surgery is used. The prognosis might be good, follow to the few data in the literature, yet the presence of scar and adherence could transform the original role of the rectus femoris.

Muscle Flap

Recent literature has shown that using the quadriceps muscle flap (vastus intermedius) is efficient for reconstructing one area the the neurocranium (after trauma or resection that tumors and for aesthetic objectives). We have no data ~ above the sensible recovery the the quadriceps muscle.

The quadriceps muscle flap deserve to be offered to fix the portion of the gluteus medius.

During prosthetic i know well implantation or a hip surgical procedure for resection the tumors or the offhanded of the insertion the the gluteus medius native the an excellent trochanter, the last muscle might be injured, compromising that function. To prevent loss the abductive duty of the hip, and in the active presence that the superior gluteal nerve, that is feasible to use a quadriceps muscle flap (generally the vastus lateralis) to develop a valuable compensation for walking.

Other basic Surgical Considerations

Any time surgery is performed, one emphasis is inserted upon recovery process. This includes an ext subtle examples, because that example, non-extremity-based surgeries choose bariatric surgery. Bariatric surgery, because that example, gastric bypass, although that may enhance physical role in general, involves a loss of mass and strength the the quadriceps muscles. This means a ns of coordination between the different vasti with boost in feasible patient falls. Muscle recovery (mass and strength) have to be bring away into factor to consider in this form of patient.

More apparent scenarios include any lower extremity surgery, including the surgeries discussed above, but also arthroscopic measures such as  anterior cruciate ligament (ACL) or posterior cruciate ligament (PCL) reconstruction.

ACL Reconstruction

Following ACL reconstruction, restore to the original role is really slow, and it is no always possible to completely recover the contractile function. Fifty percent of the athletes who undergo surgery execute not go back to previous performance levels; that the latter, around 20% to 30% will resort come a 2nd operation or build osteoarthritis problems over a duration of 10 years.

Several rehabilitative philosophies are used to regain the duty of the quadriceps, however they are not always effective, such together isokinetic, electrostimulation, or exercises that try to segment the work on each vastus muscle.

In reality, it is vital to execute exercises that reflect the attributes of the muscle, both together a range of motions (movements capable of exhaustively exploiting shortening and full elongation) and also as a usual neuromotor treatment (athletic gesture or day-to-day gesture, there is no non-physiological stimuli such as isokinetic or electrostimulation).

Furthermore, the various metabolic framework of the muscle need to be considered, such as red fibers and also white fibers. For the restore of strength, coordination, and muscle mass, one should incorporate strength cultivate exercises; while for aerobic metabolism and also endurance exercises, one does no exclude the other.

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PCL Reconstruction

After the surgical reconstruction of the posterior cruciate ligament, the useful recovery that the quadriceps is faster, although over there is incomplete restore of strength and muscle mass. One theory is that the proprioceptive afferents the the hurt anterior cruciate ligament are not able to send adequate info to the main nervous system compared to the posterior ligament. Probably, there would certainly be a better receptor intricacy for the anterior ligament in relationship to the duty of the quadriceps muscle.