Learning Objectives
- Identify the appendicular muscles of the pelvic girdle and lower limb
- Identify the movement and function of the pelvic girdle and lower limb
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 Region Muscles That Move the Femur
Most muscles that insert on the femur (the thigh bone) and move it, originate on the pelvic girdle. The psoas major and iliacus make up the iliopsoas group. Some of the largest and most powerful muscles in the body are the gluteal muscles or gluteal group. The gluteus maximus is the largest; deep to the gluteus maximus is the gluteus medius, and deep to the gluteus medius is the gluteus minimus, the smallest of the trio (Figure 1 and Table 1).
Table 1. Gluteal Region Muscles That Move the Femur | ||||
---|---|---|---|---|
Movement | Target motion direction | Prime mover | Origin | Insertion |
Iliopsoas group | ||||
raises the knee at the hip, as if performing a knee attack; it also assists the lateral rotators in twisting the thigh (and lower leg) outward, and assists with bending over and maintaining posture | thigh: flexion and lateral rotation; torso: flexion |
psoas major | lumbar vertebrae (L1 through L5) and thoracic vertebra (T12) | lesser trochanter of femur |
raises the knee at the hip, as if performing a knee attack; it also assists the lateral rotators in twisting the thigh (and lower leg) outward, and assists with bending over and maintaining posture | thigh: flexion and lateral rotation; torso: flexion |
iliacus | iliac fossa, iliac crest, and lateral sacrum | lesser trochanter of femur |
Gluteal group | ||||
lowers the knee and moves the thigh back, as when getting ready to kick a ball | extension | gluteous maximus | dorsal ilium, sacrum, and coccyx | gluteal tuberosity of femur; iliotibial tract |
opens the thigh, as when doing a split | abduction | gluteus medius | lateral surface of the ilium | greater trochanter of femur |
brings the thighs back together | abduction | gluteus minimus | external surface of the ilium | greater trochanter of femur |
assists with raising the knee at the hip and opening the thighs; it also maintains posture by stabilizing the iliotibial track, which connects to the knee | flexion; abduction | tensor fascia lata | anterior aspect of the iliac crest and the anterior superior iliac spine | iliotibial tract |
Lateral rotators | ||||
twists the thigh (and lower leg) outward; it also maintains posture by stabilizing the hip joint | lateral rotation | piriformis | anterolateral surface of the sacrum | greater trochanter of femur |
twists the thigh (and lower leg) outward; it also maintains posture by stabilizing the hip joint | lateral rotation | obturator internus | inner surface of the obturator membrane, the greater sciatic notch, and the margins of the obturator foramen | greater trochanter in front of piriformis |
twists thigh (and lower leg) outward; maintains posture by stabilizing hip joint | lateral rotation | obturator externus | outer surfaces of obturator membrane, pubic, and ischium; margins of obturator foramen | trochanteric fossa of posterior femur |
twists the thigh (and lower leg) outward; it also maintains posture by stabilizing the hip joint | lateral rotation | superior gemellus | ischial spine | greater trochanter of femur |
twists the thigh (and lower leg) outward; it also maintains posture by stabilizing the hip joint | lateral rotation | inferior gemellus | ischial tuberosity | greater trochanter of femur |
twists the thigh (and lower leg) outward; it also maints posture by stabilizing the hip joint | lateral rotation | quatratus femoris | ischial tuberosity | trochanteric crest of femur |
Adductors | ||||
brings the thighs back together; it also assists with raising the knee | adduction; flexion | adductor longus | pubis near the pubic symphysis | linea aspera |
brings the thighs back together; it also assists with raising the knee | adduction; flexion | adductor brevis | body of the pubis and in the inferior ramus of the pubis | linea aspera above adductor longus |
brings the thighs back together; it also assists with raising the knee and moving the thigh back | adduction; flexion; extension | adductor magnus | ischial rami, the pubic rami, and the ischial tuberosity | linea aspera; adductor tubercle of femur |
opens the thigh; with raising the knee and turning the thigh (and lower leg) inward | adduction; flexion; medial rotation | pectineus | pectineal line of the pubis | lesser trochanter to linea aspera of posterior aspect of femur |
The tensor fascia lata is a thick, squarish muscle in the superior aspect of the lateral thigh. It acts as a synergist of the gluteus medius and iliopsoas in flexing and abducting the thigh. It also helps stabilize the lateral aspect of the knee by pulling on the iliotibial tract (band), making it taut. Deep to the gluteus maximus, the piriformis, obturator internus, obturator externus, superior gemellus, inferior gemellus, and quadratus femoris laterally rotate the femur at the hip.
The adductor longus, adductor brevis, and adductor magnus can both medially and laterally rotate the thigh depending on the placement of the foot. The adductor longus flexes the thigh, whereas the adductor magnus extends it. The pectineus adducts and flexes the femur at the hip as well. The pectineus is located in the femoral triangle, which is formed at the junction between the hip and the leg and also includes the femoral nerve, the femoral artery, the femoral vein, and the deep inguinal lymph nodes.
Thigh Muscles That Move the Femur, Tibia, and Fibula
Deep fascia in the thigh separates it into medial, anterior, and posterior compartments (see Figure 1 and Table 2). The muscles in the medial compartment of the thigh are responsible for adducting the femur at the hip. Along with the adductor longus, adductor brevis, adductor magnus, and pectineus, the strap-like gracilis adducts the thigh in addition to flexing the leg at the knee.
Table 2. Thigh Muscles That Move the Femur, Tibia, and Fibula | |||||
---|---|---|---|---|---|
Movement | Target | Target motion direction | Prime mover | Origin | Insertion |
Medial compartment of thigh | |||||
moves the back of the lower legs up toward the buttocks, as when kneeling; it also assists in opening the thighs | femur; tibia/fibula | tibia/fibula: flexion; thigh: adduction |
gracilis | inferior ramus, the body of the pubis, and the ischial ramus | medial surface of tibia |
Anterior compartment of the thigh: Quadriceps femoris group | |||||
moves the lower leg out in front of the body, as when kicking; it also assists in raising the knee | femur; tibia/fibula | tibia/fibula: extension; thigh: flexion |
rectus femoris | anterior inferior iliac spine and in the superior margin of the acetabulum | patella; tibial tuberosity |
moves the lower leg out in front of the body, as when kicking | tibia/fibula | extension | vastus lateralis | greater trochanter, the intertrochanteric line, and the linea aspera | patella; tibial tuberosity |
moves the lower leg out in front of the body, as when kicking | tibia/fibula | extension | vastus medialis | linea aspera and the intertrochanteric line | patella; tibial tuberosity |
moves the lower leg out in front of the body, as when kicking | tibia/fibula | extension | vastus intermedius | proximal femur shaft | patella; tibial tuberosity |
moves the back of the lower legs up and back toward the buttocks, as when kneeling; it also assists in moving the thigh diagonally upward and outward as when mounting a bike | femur; tibia/fibula | tibia: flexion; thigh: flexion, abduction, lateral rotation |
sartorius | anterior superior iliac spine | medial aspect of proximal tibia |
Posterior compartment of the thigh: Hamstring group | |||||
moves the back of the lower leg up and back toward the buttocks, as when kneeling; it also moves the thigh down and back and twists the thigh (and lower leg) outward | femur; tibia/fibula | tibia/fibula: flexion; thigh: extension, lateral rotation |
biceps femoris | ischial tuberosity, linea aspera, and distal femur | head of fibula; lateral condyle of tibia |
moves the back of the lower legs up toward the buttocks, as when kneeling; it also moves the thigh down and back and twists the thigh (and lower leg) inward | femur; tibia/fibula | tibia/fibula: flexion; thigh: extension, medial rotation |
semitendinosus | ischial tuberosity | upper tibial shaft |
moves the back of the lower legs up and back toward the buttocks, as when kneeling; it also moves the thigh down and back and twists the thigh (and lower leg) inward | femur; tibia/fibula | tibia/fibula: flexion; thigh: extension, medial rotation |
semi-membranosus | ischial tuberosity | medial condyle of tibia; lateral condyle of femur |
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. 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. 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. 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.
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. These are the biceps femoris,semitendinosus, and semimembranosus. The tendons of these muscles form the popliteal fossa, the diamond-shaped space at the back of the knee.
Muscles That Move the Feet and Toes
Similar to the thigh muscles, the muscles of the leg are divided by deep fascia into compartments, although the leg has three: anterior, lateral, and posterior (Figure 2 and Table 3).
Table 3. Muscles That Move the Feet and Toes | |||||
---|---|---|---|---|---|
Movement | Target | Target motion direction | Prime mover | Origin | Insertion |
Anterior compartment of the leg | |||||
Raises the sole of the foot off the ground, as when preparing to foot-tap; bends the inside of the foot upwards, as when catching your balance while falling laterally toward the opposite side as the balancing foot | foot | dorsiflexion; inversion | tibialis anterior | lateral condyle and upper tibial shaft; interosseous membrane | interior surface of medial cuneiform; first metatarsal bone |
raises the sole of the foot off the ground, as when preparing to foot-tap; extends the big toe | foot; big toe | foot: dorsiflexion; big toe: extension |
extensor hallucis longus | anteromedial fibula shaft and interosseous membrane | distal phalanx of big toe |
raises the sole of the foot off the ground, as when preparing to foot-tap; extends the toes | foot; toes 2–5 | foot: dorsiflexion; toes: extension |
extensor digitorum longus | lateral condyle of the tibia, the proximal portion of the fibula, and the interosseous membrane | middle and distal phalanges of toes 2–5 |
Lateral compartment of the leg | |||||
lowers the sole of the foot to the ground, as when foot-tapping or jumping; it also bends the inside of the foot downwards, as when catching your balance while falling laterally toward the same side as the balancing foot | foot | plantar flexion and eversion | fibularis longus | upper portion of the lateral fibula | first metatarsal; medial cuneiform |
lowers the side of the foot to the ground, as when foot-tapping or jumping; it also bends the inside of the foot downward, as when catching your balance while falling laterally toward the same side as the balancing foot | foot | plantar flexion and eversion | fibularis (peroneus) brevis | distal fibula shaft | proximal end of fifth metatarsal |
Posterior compartment of leg: Superficial muscles | |||||
lowers the sole of the foot to the ground, as when foot-tapping or jumping; it also assists in moving the back of the lower legs up and back toward the buttocks | foot; tibia/fibula | foot: plantar flexion; tibia/fibula: flexion |
gastrocnemius | medial and lateral condyles of the femur | posterior calcaneus |
lowers the sole of the foot the ground, as when foot-tapping or jumping; it also maintains posture while walking | foot | plantar flexion | soleus | superior tibia, fibula, and interosseous membrane | posterior calcaneus |
lowers the sole of the foot to the ground, as when foot-tapping or jumping; it also assists in moving the back of the lower legs up and back toward the buttocks | foot; tibia/fibula | foot: plantar flexion; tibia/fibula: flexion |
plantaris | posterior femur above the lateral condyle | calcaneus or calcaneus tendon |
lowers the sole of the foot to the ground, as when foot-tapping or jumping | foot | plantar flexion | tibialis posterior | superior tibia and fibula and in the interosseous membrane | several tarsals and metatarsals 2–4 |
Posterior compartment of the leg: Deep muscles | |||||
moves the back of the lower legs up and back toward the buttocks; it also assists in rotation of the leg at the knee and thigh | tibia/fibula | tibia/fibula: flexion; thigh and lower leg: medial and lateral rotation |
popliteus | lateral condyle of the femur and the lateral meniscus | proximal tibia |
lowers the sole of the foot to the ground, as when foot-tapping or jumping; it also bends the inside of the foot upward and flexes the toes | foot; toes 2–5 | foot: plantar flexion and inversion; toes: flexion |
flexor digitorum longus | posterior tibia | distal phalanges of toes 2–5 |
flexes the big toe | big toe; foot | big toe: flexion; foot: plantar flexion |
flexor hallicis longus | midshaft of fibula; interosseous membrane | distal phalanx of big toe |
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. The fibularis tertius, a small muscle that originates on the anterior surface of the fibula, is associated with the extensor digitorum longus and sometimes fused to it, but is not present in all people. Thick bands of connective tissue called the superior extensor retinaculum (transverse ligament of the ankle) and the inferior extensor retinaculum, hold the tendons of these muscles in place during dorsiflexion.
The lateral compartment of the leg includes two muscles: the fibularis longus (peroneus longus) and the fibularis brevis (peroneus brevis). 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 calcaneal bone of the ankle. The muscles in this compartment are large and strong and keep humans upright. The most superficial and visible muscle of the calf is the gastrocnemius. Deep to the gastrocnemius is the wide, flat soleus. The plantaris runs obliquely between the two; some people may have two of these muscles, whereas no plantaris is observed in about seven percent of other cadaver dissections. The plantaris tendon is a desirable substitute for the fascia lata in hernia repair, tendon transplants, and repair of ligaments. There are four deep muscles in the posterior compartment of the leg as well: the popliteus, flexor digitorum longus, flexor hallucis longus, and tibialis posterior.
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 (Figure 3 and Table 4). 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. The intrinsic muscles of the foot consist of two groups. The dorsal group includes only one muscle, the extensor digitorum brevis. The second group is the plantar group, which consists of four layers, starting with the most superficial.
Table 4. Intrinsic Muscles in the Foot | |||||
---|---|---|---|---|---|
Movement | Target | Target motion direction | Prime mover | Origin | Insertion |
Dorsal group | |||||
extends toes 2 through 5 | toes 2–5 | extension | extensor digitorum brevis | calcaneus; extensor retinaculum | base of proximal phalanx of big toe; extensor expansions on toes 2–5 |
Plantar group (layer 1) | |||||
abducts and flexes the big toe | big toe | adduction; flexion | abductor hallucis | calcaneal tuberosity; flexor retinaculum | proximal phalanx of big toe |
flexes toes 2 through 4 | middle toes | flexion | flexor digitorum brevis | calcaneal tuberosity | middle phalanx of toes 2–4 |
abducts and flexes the small toe | toe 5 | abduction; flexion | abductor digiti minimi | calcaneal tuberosity | proximal phalanx of little toe |
Plantar group (layer 2) | |||||
assists in flexing toes 2 through 5 | toes 2–5 | flexion | quadratus plantae | medial and lateral sides of the calcaneus | tendon of flexor digitorum longus |
extend toes 2 through 5 at the interphalangeal joints; they also flex the small toes at the metatarsophalangeal joints | toes 2–5 | extension; flexion | lumbricals | tendons of the flexor digitorum longus | medial side of proximal phalanx of toes 2–5 |
Plantar group (layer 3) | |||||
flexes the big toe | big toe | flexion | flexor hallucis brevis | lateral cuneiform and in the cuboid bones | base of proximal phalanx of big toe |
adducts and flexes the big toe | big toe | adduction; flexion | adductor hallucis | bases of metatarsals 2 through 4, in the fibularis longus tendon sheath, and in the ligament across the metatarsophalangeal joints | base of proximal phalanx of big toe |
flexes the small toe | little toe | flexion | flexor digiti minimi brevis | base of metatarsal 5 and in the tendon sheath of the fibularis longus | base of proximal phalanx of little toe |
Plantar group (layer 4) | |||||
abducts and flexes the middle toes at the metatarsophalangeal joints; it also extends the middle toes at the interphalangeal joints | middle toes | abduction; flexion; extension | dorsal interossei | sides of the metatarsals | both sides of toe 2; for each tother to, extensor expansion over first phalanx on side opposite toe 2 |
abducts toes 3 through 5; it also flexes the proximal phalanges and extends the distal phalanges | small toes | abduction; flexion; extension | plantar interossei | side of each metatarsal that faces metatarsal 2 (absent from metatarsal 2) | extensor expansion on first phalanx of each toe (except toe 2) on side facing toe 2 |
Self-Check Questions
Take the quiz below to check your understanding of the Appendicular Muscles of the Pelvic Girdle and Lower Limbs: