Muscles and Muscle ActionLower Extremities

Muscles that Move…• The Lower Extremities:• The Coxal joint/thigh• Thigh muscles that move the knee joint/leg• Leg muscles• Intrinsic muscles of the foot

The Muscles of the Coxal Joint/Thigh• Anterior Thigh Compartment (Thigh Flexors)• Medial Thigh Compartment (Thigh Adductors)• Lateral Thigh Compartment (Thigh Abductors)• Gluteal Group• Deep Muscles of the Gluteal Region (Lateral Thigh Adductors)• Posterior Thigh (Hamstring) Compartment (Thigh Extensors

and Leg Flexors)

Muscles of the Anterior Thigh Compartment (thigh flexors)• Psoas Major• Flexes and laterally rotates thigh

• Iliacus• Flexes and laterally rotates thigih

• Sartorius• Flexes thigh and rotates thigh laterally; flexes leg and rotates leg

medially• Rectus Femoris• Extends leg; flexes thigh

Muscles of the Medial Thigh Compartment (thigh adductors)• Adductor Longus• Adducts thigh; flexes thigh

• Adductor Brevis• Adducts thigh

• Gracilis• Adducts and flexes thigh; flexes leg

• Pecineus• Adducts thigh; flexes leg

• Adductor Magnus• Adducts thigh; adductor part of muscle flexes thigh; hamstring

part of muscle extends and laterally rotates thigh• Obturator Externus• Laterally rotates thigh

Muscles of the Lateral Thigh Compartment (thigh abductor)• Tensor Fasciae Latae• Abducts thigh’ medially rotates thigh

Muscles of the Gluteal Group• Gluteus Maximus• Extends thigh; laterally rotates thigh

• Gluteus Medius• Abducts thigh; medially rotates thigh

• Gluteus Minimus• Abducts thigh; medially rotates thigh

Muscles of the Deep Gluteal Region (lateral thigh rotators)• Piriformis• Laterally rotates thigh

• Superior Gemellus• Laterally rotates thigh

• Obturator Internus• Laterally rotates thigh

• Inferior Gemellus• Laterally rotates thigh

• Quadratus Femoris• Laterally rotates thigh

Muscles of the Posterior Thigh (hamstring) Compartment• Biceps Femoris• Extends thigh (long head only); flexes leg (both long head and

short head); laterally rotates leg• Semimembranosus• Extends thigh and flexes leg; medially rotates leg

• Semitendinosus• Extends thigh and flexes leg; medially rotates leg

The Thigh Muscles That Move the Knee Joint/Leg• Leg Extensors

• Quadriceps Femoris• Rectus Femoris

• Extends leg; flexes thigh• Vastus Intermedius

• Extends leg• Vastus Lateralis

• Extends leg• Vastus Medius

• Extends leg

• Leg Flexors• Sartorius

• Flexes thigh and rotates thigh laterally; flexes leg and rotates thigh medially• Gracilis

• Flexes and adducts thigh; flexes leg• Biceps Femoris

• Extend thigh and flex leg; rotate leg laterally• Semimembranosus

• Extend thigh and flex leg; rotate leg medially• Semitendinosus

• Extend thigh and flex leg; rotates leg medially

Leg Muscles• Anterior Compartment (dorsiflexors and toe extensors)• Lateral Compartment (evertors and weak plantar flexors)• Posterior Compartment (plantar flexors, flexors of the leg and

toes)• Superficial Layer• Deep Layer

Leg Muscles: Anterior Compartment• Extensor Digitorum Longus• Extends toes 2-5

• Extensor Hallucis Longus• Extends great toe; dorsiflexes foot

• Fibularis Tertius• Dorsiflexes and weakly everts foot

• Tibialis Anterior• Dorsiflexes foot; Inverts foot

Leg Muscles: Lateral Compartment• Fibularis Longus• Everts foot, weak plantar flexor

• Fibularis Brevis• Everts Foot, weak plantar flexor

Leg Muscles: Posterior Compartment• Superficial:• Triceps Surae

• Gastrocnemius• Flexes leg; plantar flexes foot

• Soleus• Plantar flexes foot

• Plantaris• Weak leg flexor and plantar flexor

• Deep:• Flexor Digitorum Longus

• Plantar flexes foot; flexes MP, PIP, and DIP joints of toes 2-5• Flexor Hallucis Longus

• Plantar flexes foot; flexes MP and IP joints of great toe• Tibialis Posterior

• Plantar flexes foot; inverts foot• Poplitus

• Flexes leg; medially rotates tibia to unlock the knee

Intrinsic Muscles of the Foot• Dorsal Surface (toe extensors)• Plantar Surface (toe flexors, adductors, abductors)• Layer 1 (superficial• Layer 2 (Deep)• Layer 3 (Deeper)• Layer 4 (Deepest)

Intrinsic Muscles of the Foot• Dorsal Surface• Extensor Hallucis Brevis

• Extends MP joint of great toe• Extensor Digitorum Brevis

• Extends MP and PIP joints of toes 2-4

Intrinsic Muscles of the Foot• Plantar Surface• Layer 1 (superficial)

• Flexor Digitorum Brevis• Flexes MP and PIP joints of toes 2-5

• Abductor Hallucis• Abducts great toe

• Abductor Digiti Minimi• Abducts toe 5

Intrinsic Muscles of the Foot• Plantar Surface• Layer 2 (Deep)

• Quadratus Plantae• Pulls on flexor digitorum longus tendons to flex toe 2-5

• Lumbricals• Flexes MP joints and extends PIP and DIP joints of toes 2-5

Intrinsic Muscles of the Foot• Plantar Surface• Layer 3 (Deeper)

• Adductor Hallucis• Adducts great toe

• Flexor Hallucis Brevis• Flexes MP joint of great toe

• Flexor Digiti Minimi Brevis• Flexes MP joint of toe 5

Intrinsic Muscles of the Foot• Plantar Surface• Layer 4 (Deepest)

• Dorsal Interossei• Abducts toes

• Plantar Interossei• Adducts toes