9.7: Appendicular Muscles of the Pelvic Girdle and Lower Limbs

By the end of this section, you will be able to:

• Identify the major appendicular muscles of the pelvic girdle and lower limb
• Identify the movement caused by these muscles

The appendicular muscles of the lower body position and stabilize the pelvic girdle, which serves as a foundation for the lower limbs. Comparatively, there is much more movement at the pectoral girdle than at the pelvic girdle. There is very little movement of the pelvic girdle because of its connection with the sacrum at the base of the axial skeleton. The pelvic girdle is less range of motion because it was designed to stabilize and support the body.

Muscles of the Thigh

What would happen if the pelvic girdle, which attaches the lower limbs to the torso, were capable of the same range of motion as the pectoral girdle? For one thing, walking would expend more energy if the heads of the femurs were not secured in the acetabula of the pelvis. The body’s center of gravity is in the area of the pelvis. If the center of gravity were not to remain fixed, standing up would be difficult as well. Therefore, what the leg muscles lack in range of motion and versatility, they make up for in size and power, facilitating the body’s stabilization, posture, and movement.

Gluteal and Pelvic Muscles That Move the Femur

Most muscles that insert on the femur (the thigh bone) and move it, originate on the pelvic girdle (Table \(\PageIndex{1}\)).

• The psoas major (the "p" is silent when pronouncing) and iliacus make up the iliopsoas group. These muscles originate on the posterior, interior of the pelvis and the vertebral column, pass over the pubis and insert into lesser trochanter of the femur. When they pass the inguinal ligament their fibers blend together so in the thigh the joined muscle is called the iliopsoas. Their anterior position relative to the hip joint makes them strong hip flexors (Figure \(\PageIndex{1}\)).
• Some of the largest and most powerful muscles in the body are the gluteal muscles or gluteal group. From superficial to deep as well as largest to smallest these three muscles are the gluteus maximus, gluteus medius, and gluteus minimus. Gluteus maximus is the prime mover of hip extension as well as a lateral rotator. The gluteus medius and minimus both abduct and medially rotate the hip (Figure \(\PageIndex{1}\)). The gluteus maximus has two insertion points: one in the posterior femur and one on the superior, lateral tibia via that iliotibial (IT) band.

Figure \(\PageIndex{1}\): Muscles - Iliopsoas and Gluteal Groups. The primary of action of these muscles is hip flexion (A. iliopsoas group) and hip extension, abduction, and rotation (B. gluteal group). (Image credits: "Iliopsoas and Gluteal Group Muscles" by Jennifer Lange are licensed under CC BY-NC-SA 4.0, based on images by University of British Columbia Clinical Anatomy)

• Also in the gluteal compartment, the tensor fasciae latae (TFL) is a thick, squarish muscle in the superior aspect of the lateral thigh. It acts as a synergist of the gluteus medius in abducting the thigh. It also helps stabilize the lateral aspect of the knee by pulling on the iliotibial tract (band), making it taut (Figure \(\PageIndex{1}\)).
• Deep to the gluteal muscles, the piriformis, superior gemellus, obturator externus, inferior gemellus, obturator internus, and quadratus femoris laterally rotate the femur at the hip (Figure \(\PageIndex{2}\)).

Figure \(\PageIndex{2}\): Muscles - Deep Gluteal Group. These small muscles stabilize the hip and help rotate it laterally. From superior to inferior they go in the the order of PG GO Q. (Image credits: "Deep Gluteal Group Muscles" by Jennifer Lange are licensed under CC BY-NC-SA 4.0, based on images by University of British Columbia Clinical Anatomy)

Muscles of the Medial Compartment

Six muscles are located in the medial compartment of the thigh (Figure \(\PageIndex{3}\)). Most of these muscles perform adduction at the hip joint, and each performs other actions as well. The adductor longus, adductor brevis, gracilis, and pectineus also flex the hip joint. Adductor magnus, depending on which fibers are activated, can flex, extend, and laterally rotate the thigh. Gracilis is the only one of this groups of muscles that does not insert into the femur, it inserts into the posterior, medial aspect of the superior tibia which also allows it to cause flexion at the knee joint. The only muscle in this compartment that does not adduct is the obturator externus, this muscle's action is to laterally rotate the hip.

Figure \(\PageIndex{3}\): Muscles - Medial Thigh Compartment. All but one of the muscles in this group cause thigh adduction because they cross the hip joint on the medial side. Image A shows the more anterior muscles, image B shows the more posterior muscles, and image C shows them all. (Image credits: "Medial Thigh Muscles" by Jennifer Lange are licensed under CC BY-NC-SA 4.0, based on images by University of British Columbia Clinical Anatomy)

Table \(\PageIndex{1}\): Muscles that Move the Hip Joint

Muscle	Origin		Insertion	Movement	Image(s)
Iliopsoas group
Iliacus	Iliac fossa; iliac crest; lateral sacrum		Lesser trochanter of femur	Flexes hip
Psoas major	Lumbar vertebrae (L1 - L5); thoracic vertebrae (T12)		Lesser trochanter of femur	Flexes hip
Gluteal Group
Gluteus maximus	Dorsal ilium; sacrum; coccyx		Gluteal tuberosity of femur; iliotibial tract	Extend and laterally rotates hip
Gluteus medius	Lateral surface of ilium		Greater trochanter of femur	Abducts and medially rotates hip
Gluteus minimus	External surface of ilium		Greater trochanter of femur	Abducts and medially rotates hip
Tensor fascia lata	Anterior aspect of iliac crest; anterior superior iliac spine		Iliotibial tract	Abducts and medially rotates hip
Deep Gluteal Muscles
Inferior gemellus	Ischial tuberosity		Greater trochanter of femur	Laterally rotates hip; maintains posture by stabilizing hip joint
Obturator externus	Outer surfaces of obturator membrane, pubis, and ischium; margins of obturator foramen		Trochanteric fossa of posterior femur	Laterally rotates hip; maintains posture by stabilizing hip joint
Obturator internus	Inner surface of obturator membrane; greater sciatic notch; margins of obturator foramen		Greater trochanter in front of piriformis	Laterally rotates hip; maintains posture by stabilizing hip joint
Piriformis	Anterolateral surface of sacrum		Greater trochanter of femur	Laterally rotates hip; maintains posture by stabilizing hip joint
Quadratus femoris	Ischial tuberosity		Trochanteric crest of femur	Laterally rotates hip; maintains posture by stabilizing hip joint
Superior gemellus	Ischial spine		Greater trochanter of femur	Laterally rotates hip; maintains posture by stabilizing hip joint
Medial Muscles
Adductor brevis	Body of pubis; inferior ramus of pubis		Linea aspera above adductor longus	Adducts and flexes hip
Adductor longus	Pubis near pubic symphysis		Linea aspera	Adducts and flexes hip
Adductor magnus	Ischial rami; pubic rami; ischial tuberosity		Linea aspera; adductor tubercle of femur	Adducts hip Posterior fibers: extends and laterally rotates hip Anterior fibers: flex hip
Gracilis	Inferior ramus; body of pubis; ischial ramus		Medial surface of tibia	Adducts and flexes hip; flexes knee
Pectineus	Pectineal line of pubis		Lesser trochanter to linea aspera of posterior aspect of femur	Adducts and flexes hip
Image Credits All images in this table are by University of British Columbia Clinical Anatomy and are licensed under CC BY-NC-SA 4.0.

Muscles of the Anterior Compartment

The muscles of the anterior compartment of the thigh flex the thigh and extend the leg. This compartment contains the quadriceps femoris group, which actually comprises four muscles that extend and stabilize the knee (Figure \(\PageIndex{4}\)). The rectus femoris is on the anterior aspect of the thigh, the vastus lateralis is on the lateral aspect of the thigh, the vastus medialis is on the medial aspect of the thigh, and the vastus intermedius is between the vastus lateralis and vastus medialis and deep to the rectus femoris. The tendon common to all four is the quadriceps tendon (patellar tendon), which inserts into the patella and continues below it as the patellar ligament. The patellar ligament attaches to the tibial tuberosity.

Figure \(\PageIndex{4}\): Muscles - Anterior Thigh. The two superficial muscles (A) act on both the hip and knee joints. The deeper muscles (B) only act on the knee joint. When all muscles are shown, the vastus intermedius cannot be seen (C) because it is deep to the rectus femoris. (Image credits: "Anterior Thigh Muscles" by Jennifer Lange are licensed under CC BY-NC-SA 4.0, based on images by University of British Columbia Clinical Anatomy)

In addition to the quadriceps femoris, the sartorius is a band-like muscle that extends from the anterior superior iliac spine to the medial side of the proximal tibia (Figure \(\PageIndex{4}\)). This versatile muscle flexes the leg at the knee and flexes, abducts, and laterally rotates the leg at the hip. This muscle allows us to sit cross-legged.

Table \(\PageIndex{2}\): Thigh Muscles That Move the Femur, Tibia, and Fibula

Muscle	Origin	Insertion	Movement	Image(s)
Anterior Compartment of Thigh: Quadricepts Femoris Group
Rectus femoris	Anterior inferior iliac spine; superior margin of acetabulum	Patella; tibial tuberosity	Moves lower leg out in front of body, as when kicking; assists in raising knee
Sartorius	Anterior superior iliac spine	Medial aspect of proximal tibia	Moves back of lower legs up and back toward the buttocks, as when kneeling; assists in moving thigh diagonally upward and outward as when mounting a bike
Vastus intermedius	Proximal femur shaft	Patella; tibial tuberosity	Moves lower leg out in front of body, as when kicking
Vastus lateralis	Greater trochanter; intertrochanteric line; linea apera	Patella; tibial tuberosity	Moves lower leg out in front of body, as when kicking
Vastus medialis	Linea aspera; intertrochanteric line	Patella; tibial tuberosity	Moves lower leg out in front of body, as when kicking
Posterior Compartment of Thigh: Hamstring Group
Biceps femoris	Ischial tuberosity; linea aspera; distal femur	Head of fibula; lateral condyle of tibia	Moves back of lower legs up and back toward the buttocks, as when kneeling; moves thigh down and back; twists the thigh (and lower leg) outward
Semimembranosus	Ischial tuberosity	Medial condyle of tibia; lateral condyle of femur	Moves back of lower legs up and back toward the buttocks, as when kneeling; moves thigh down and back; twists the thigh (and lower leg) outward
Semitendinosus	Ischial tuberosity	Upper tibial shaft	Moves back of lower legs up and back toward the buttocks, as when kneeling; moves thigh down and back; twists the thigh (and lower leg) outward
Image Credits All images in this table are by University of British Columbia Clinical Anatomy and are licensed under CC BY-NC-SA 4.0.

Muscles of the Posterior Compartment

The posterior compartment of the thigh includes muscles that flex the leg and extend the thigh. The three long muscles on the back of the knee are the hamstring group, which flexes the knee and extends the hip. These are the biceps femoris (long head), semitendinosus, and semimembranosus. The biceps femoris also has a short head that is not considered part of the hamstrings because it only flexes the knee and does not extend the hip (Figure \(\PageIndex{5}\)). The tendons of these muscles form the popliteal fossa, the diamond-shaped space at the back of the knee.

Figure \(\PageIndex{5}\): Muscles - Posterior Thigh. The superficial (A) and deep (B) muscles of the hamstring group cross both the hip and the knee joints. The short head of the biceps femoris (B) is not considered a hamstring because it does not do both of these functions, but it is located in the posterior thigh. When all muscles are shown, the short head cannot be seen (C) because it is deep to the long head. (Image credits: "Posterior Thigh Muscles" by Jennifer Lange are licensed under CC BY-NC-SA 4.0, based on images by University of British Columbia Clinical Anatomy)

Muscles That Move the Feet and Toes

The muscles that move the ankle, foot, and toes and are located in the leg are called the crural muscles. Similar to the thigh muscles, the muscles of the leg are divided by fascia into compartments, although the leg has three: anterior, lateral, and posterior (Table \(\PageIndex{3}\)).

Muscles of the Anterior Compartment

The muscles in the anterior compartment of the leg: the tibialis anterior, a long and thick muscle on the lateral surface of the tibia, the extensor hallucis longus, deep under it, and the extensor digitorum longus, lateral to it, all contribute to raising the front of the foot when they contract. Some, but not all, people have a third muscle in this group called the fibularis tertius (tertius="third"), a small muscle that originates on the anterior surface of the fibula, is associated with the extensor digitorum longus and sometimes fused to it (Figure \(\PageIndex{6}\)).

Figure \(\PageIndex{6}\): Muscles - Anterior Leg. The superficial (A) and deep (B) muscles of the anterior compartment of the leg cross both the ankle and joints in the foot. When all muscles are shown, only a small piece of the deep muscles can be seen (C), but you can easily identify the extensor hallicus longus because its tendon can be traced from the big toe. (Image credits: "Anterior Leg Muscles" by Jennifer Lange are licensed under CC BY-NC-SA 4.0, based on images by University of British Columbia Clinical Anatomy)

Muscles of the Lateral Compartment

The lateral compartment of the leg includes two muscles: the fibularis longus (aka peroneus longus) and the fibularis brevis (aka peroneus brevis) (Figure \(\PageIndex{7}\)). Fibularis longus is the more superficial of the two and it originates more proximally on the fibula than does the fibularis brevis. Both are strong everters of the foot and weak plantar flexors.

Figure \(\PageIndex{7}\): Muscles - Lateral Leg. The two muscles in the lateral compartment of the leg run along the length of the fibula (A). Based on their insertion points (B), both muscles cause eversion of the foot. (Image credits: "Lateral Leg Muscles" by Jennifer Lange are licensed under CC BY-NC-SA 4.0, based on images by University of British Columbia Clinical Anatomy)

Muscles of the Posterior Compartment

The superficial muscles in the posterior compartment of the leg all insert onto the calcaneal tendon (Achilles tendon), a strong tendon that inserts into the posterior aspect of the calcaneaus, and all are plantar flexors of the ankle joint. The most superficial and visible muscle of the calf is the gastrocnemius. This muscle originates superior to the knee and inserts into the calcaneous, so it is responsible for both knee flexion and ankle plantar flexion. The gastrocnemius has two wide muscle bellies called the medial head and the lateral head. Deep to the gastrocnemius is the wide, flat soleus. This muscle is named because it resembles a flatfish. The two heads of the gastrocnemius together with the soleus are collectively called the triceps surae or, more commonly, the calf muscles. The plantaris is a small muscle with a long tendon that runs obliquely between the two large sural muscles; some people may have two of these muscles, whereas no plantaris is observed in about seven percent of other cadaver dissections.

Figure \(\PageIndex{8}\): Posterior Leg Muscles. Superficial (A) and deep (B) views of the posterior compartment of the leg showing the muscles that plantar flex the ankle, invert the foot, and flex the toes as well as their tendinous insertions (C). (Image credits: "Posterior Leg Muscles" by Jennifer Lange are licensed under CC BY-NC-SA 4.0, based on images by University of British Columbia Clinical Anatomy)

There are four deep muscles in the posterior compartment of the leg: the flexor digitorum longus, flexor hallucis longus, tibialis posterior and popliteus. Popliteus is a small muscle that runs diagonally across the popliteal region. Its main function is to "unlock" the knee joint through slight medial rotation and flexion. The three remaining muscles are located along the posterior surface of the tibia and the fibula, deep to the triceps surae (Figure \(\PageIndex{8}\)). All plantarflex the ankle joint. As their names suggest, flexor digitorum longus also flexes digits 2-5 and flexor hallucis longus also flexes the big toe. The secondary action of the tibialis posterior is inversion of the foot. The commonly used neumonic for the order of the tendons of these three muscles as they pass posterior to the medial malleolus is Tom, Dick, And Very Nervous Harry: T = Tibialis posterior, Dick = flexor Digitorum longus, A = artery, V = vein, N = nerve, H = flexor Hallicus longus.

Table \(\PageIndex{3}\): Muscles That Move the Feet and Toes

Prime Mover	Origin	Insertion	Movement	Image(s)
Anterior Compartment of Leg
Extensor digitorum longus	Lateral condyle of tibia; proximal portion of fibula; interosseous membrane	Middle and distal phalanges of toes 2 - 5	Extends toes 2-4; dorsiflexion of ankle
Extensor hallucis longus	Anteromedial fibula shaft; interosseous membrane	Distal phalanx hallux (big toe)	Extends the big toe; dorsiflexion of ankle
Tibialis anterior	Lateral condyle and upper tibial shaft; interosseous membrane	Interior surface of medial cuneiform; first metatarsal bone	Dorsiflexion of ankle; inversion of intertarsal
Lateral Compartment of Leg
Fibularis (peroneus) brevis	Distal fibula shaft	Proximal end of fifth metatarsal	Eversion of intertarsal; plantarflexion of ankle
Fibularis (peroneus) longus	Upper portion of lateral fibula	First metatarsal; medial cuneiform	Eversion of intertarsal, plantarflexion of ankle
Posterior Compartment of Leg: Superficial Muscles
Gastrocnemius	Medial and lateral condyles of femur	Posterior calcaneus	Plantarflexion of ankle; flexion of knee
Soleus	Superior tibia; fibula; interosseous membrane	Posterior calcaneus	Plantarflexion of ankle
Posterior Compartment of Leg: Deep Muscles
Flexor digitorum longus	Posterior tibia	Distal phalanges of toes 2 - 5	Flexion of digits 2-5; plantarflexion of ankle
Flexor hallucis longus	Midshaft of fibula; interosseous membrane	Distal phalanx of hallux (big toe)	Flexes big toe; plantarflexion of ankle
Tibialis posterior	Superior tibia; fibula; interosseous membrane	Tarsals and metatarsals 2 - 4	Plantarflexion of ankle; inversion of intertarsal
Image Credits All images in this table are by University of British Columbia Clinical Anatomy and are licensed under CC BY-NC-SA 4.0.

The foot also has intrinsic muscles, which originate and insert within it (similar to the intrinsic muscles of the hand). These muscles primarily provide support for the foot and its arch, and contribute to movements of the toes. The principal support for the longitudinal arch of the foot is a deep fascia called plantar aponeurosis, which runs from the calcaneus bone to the toes (inflammation of this tissue is the cause of “plantar fasciitis,” which can affect runners. 

Muscles of the lower limb

Explore the muscles of the lower limb in this 3D rending of a human leg model.

 

Human Leg by AnatomyPhysiologySCC on Sketchfab

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Concept Review

The pelvic girdle attaches the legs to the axial skeleton. The hip joint is where the pelvic girdle and the leg come together. The hip is joined to the pelvic girdle by many muscles. In the gluteal region, the psoas major and iliacus form the iliopsoas. The large and strong gluteus maximus, gluteus medius, and gluteus minimus extend and abduct the femur. Along with the gluteus maximus, the tensor fascia lata muscle forms the iliotibial tract. The lateral rotators of the femur at the hip are the piriformis, obturator internus, obturator externus, superior gemellus, inferior gemellus, and quadratus femoris. On the medial part of the thigh, the adductor longus, adductor brevis, and adductor magnus adduct the thigh and medially rotate it. The pectineus muscle adducts and flexes the femur at the hip.

The thigh muscles that move the femur, tibia, and fibula are divided into medial, anterior, and posterior compartments. The medial compartment includes the adductors, pectineus, and the gracilis. The anterior compartment comprises the quadriceps femoris, quadriceps tendon, patellar ligament, and the sartorius. The quadriceps femoris is made of four muscles: the rectus femoris, the vastus lateralis, the vastus medius, and the vastus intermedius, which together extend the knee. The posterior compartment of the thigh includes the hamstrings: the biceps femoris, semitendinosus, and the semimembranosus, which all flex the knee.

The muscles of the leg that move the foot and toes are divided into anterior, lateral, superficial- and deep-posterior compartments. The anterior compartment includes the tibialis anterior, the extensor hallucis longus, the extensor digitorum longus, and the fibularis (peroneus) tertius. The lateral compartment houses the fibularis (peroneus) longus and the fibularis (peroneus) brevis. The superficial posterior compartment has the gastrocnemius, soleus, and plantaris; and the deep posterior compartment has the popliteus, tibialis posterior, flexor digitorum longus, and flexor hallucis longus.

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Review Questions

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Critical Thinking Questions

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Glossary

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Contributors and Attributions

• OpenStax Anatomy & Physiology (CC BY 4.0). Access for free at https://openstax.org/books/anatomy-and-physiology