Download Lower Extremity Muscle Actions

Knee Muscle Actions
Knee Extension (Concentric)
 Quads (Rectus Femoris, Vastus Lateralis, Vastus Medialis, Vastus Intermedius)
 (Rectus Femoris – Also flexes hip!!!)
Knee Flexion (Concentric)
 Hamstrings (Biceps Femoris, Semitendinosus, Semimembranosus)
(Hamstrings –except for short head of biceps femoris -also extend hip!!!)
 Sartorius, Gracilis (a little)
(Sartorius also externally rotates & flexes hip (as when crossing your leg)!!!)
(Gracilis also adducts the hip!!!)
 Gastrocnemius
 Plantaris (minimal)
Unlocks Knee
 Popliteus
(externally rotates femur if foot is planted; internally rotates tibia if foot is free)
Pulls Synovial Membrane Superiorly During Knee Extension
 Articularis Genu
Gluteals
Tensor fascia lata

Action:
1. hip flexion
2. medially rotate & abduct a flexed thigh
3. tenses IT tract to support femur on the tibia during standing
Gluteus medius & minimus
 Action:
1. anterior and lateral fibers abduct and medially rotate the thigh
2. stabilizes the pelvis and prevents free limb from sagging during gait
Gluteus maximus

Action:
1. powerful extensor of hip
2. laterally rotates thigh
3. upper fibers aid in abduction of thigh
4. fibers of IT band stabilize a fully extended knee
Piriformis, Superior Gemellus, Obturator Internus

Action:
1. lateral rotation of extended thigh
2. abducts a flexed thigh
Inferior gemellus & Quadratus femoris
 Action: laterally rotates femur
Posterior Thigh Musculature
Semitendinosus

Action:
1. extends hip
2. flexes knee
3. medially rotates tibia
Semimembranosus

Action:
1. flexes knee
2. extends hip
3. medially rotates tibia
4. pulls medial meniscus posterior during flexion
Biceps femoris

Action:
1. flexes knee (mainly short head)
2. laterally rotates thigh if flexed at the knee
3. extends hip (long head)
Adductor Thigh Musculature
Adductor longus

Action:
1. adducts thigh
2. flexes thigh
3. may laterally rotate thigh at the hip
Adductor brevis

Action:
1. adducts thigh (major)
2. aids in flexion of thigh
3. may laterally rotate thigh at the hip
Adductor magnus

Action:
1. adducts the thigh
2. posterior fibers also extend and laterally rotate thigh
Gracilis

Action:
1. adducts thigh
2. flexes knee
3. medially rotates tibia
Obturator externus

Action:
1. laterally rotates thigh
2. assists in flexion of hip joint
Anterior Thigh Musculature
Sartorius

Action:
1. flexes hip and knee
2. laterally rotates thigh if flexed at the hip
Rectus femoris

Action:
1. extends knee
2. flexes hip
Vastus lateralis

Action:
1. extends knee
2. can laterally displace patella
Vastus intermedius

Action: extends knee
Vastus medialis

Action: extends knee
Articularis genus

Action:
1. pulls the synovial membrane of the knee superior with knee extension
2. prevents impingement of the synovial membrane between patella and the femur
Psoas major

Action:
1. hip flexion
2. lateral rotation
Illiacus

Action:
1. powerful hip flexion
2. lateral rotation
Pectineus

Action:
1. flexes hip
2. adducts thigh
3. medially rotates thigh
Posterior Leg Musculature
Gastrocnemius
o
Action:
1. plantarflex the ankle
2. knee flexion (when not weight bearing)
3. stabilizes ankle & knee when standing
Soleus
o
Action: plantarflex the foot
Plantaris
o
Action: like a weak gastrocnemius
Popliteus
o
Action:
1. insertion fixed: laterally rotates femur on tibia & unlocks knee
2. origin fixed: medially rotates tibia on femur & unlocks knee
Flexor digitorum longus
o
Action:
1. primarily flexes 2nd - 5th toes
2. weak plantarflexor
3. weak inversion & adduction of foot
Tibialis posterior

Action:
1. stabilizes ankle
2. inversion & adduction of foot
3. prevents hyperpronation while in gait
4. weak plantarflexion of ankle
Flexor hallucis longus
o
Action:
1. flexes big toe (hallux)
2. weak plantarflexion of the foot
3. weak inversion & adduction of foot
Anterolateral Leg Musculature
Peroneus longus
o
Action:
1. eversion & abduction of the foot
2. weak plantarflexion of the foot at the transverse tarsal joint
Peroneus brevis
o
Action:
1. eversion & abduction of the foot
2. weak plantarflexion of foot
Tibialis anterior
o
Action:
1. strongest dorsiflexor
2. inverts & adducts the foot
Extensor hallucis longus
o
Action:
1. extends distal phalanx of big toe
2. weak dorsiflexor
3. weak inversion & adduction
Extensor digitorum longus
o
Action:
1. extends the lateral 4 toes
2. weak dorsiflexor & everts foot
Peroneus tertius
o
Action:
1. extends the 5th toe
2. weak dorsiflexor & everts foot
Posterior Right Leg Muscles
Anterior Right Leg Muscles
Refer to the above diagrams of leg muscles for the following questions:
Diagrams taken from http://www.exrx.net/Lists/Directory.html on April 25, 2008 ExRx.net Exercise & Muscle Directory
On the Anterior Right Leg Muscles diagram the letter a is on what muscle? Tensor Fascia Latae
On the Anterior Right Leg Muscles diagram the letter l is on what tendinous structure?
Iliotibial Band (IT Band)
On the Anterior Right Leg Muscles diagram the letter b is on what muscle? Vastus Lateralis
On the Anterior Right Leg Muscles diagram the letter c is on what muscle? Rectus Femoris
On the Anterior Right Leg Muscles diagram the letter d is on what muscle? Vastus Medialis
On the Anterior Right Leg Muscles diagram the letter e is on what muscle? Sartorius
On the Anterior Right Leg Muscles diagram the letter j is on what bony structure? Patella
On the Anterior Right Leg Muscles diagram the letter m is on what bony structure? Head of the
fibula
On the Anterior Right Leg Muscles diagram the letter n is on what bone? Tibia
On the Anterior Right Leg Muscles diagram the letter k is on what bony structure? Tibial
Tuberosity
On the Anterior Right Leg Muscles diagram the letter j is connected to the letter k by what
structure? The patellar tendon or patellar ligament
On the Posterior Right Leg Muscles diagram the letter j is on what muscle? Gracilis
On the Posterior Right Leg Muscles diagram the letter m is over what area? Popliteal fossae
On the Posterior Right Leg Muscles diagram the letter d is on what tendinous structure?
Iliotibial Band (IT Band)
On the Posterior Right Leg Muscles diagram the number 1 is on what muscle? Biceps Femoris
On the Posterior Right Leg Muscles diagram the number 3 is on what muscle? Semitendinosis
On the Posterior Right Leg Muscles diagram the number 4 is on what muscle?
Semimembranosis
On the Posterior Right Leg Muscles diagram the letter b is on what muscle? Gluteus Medius
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