Muscles of the Lower Limb: Structure, Function, Attachments, and Innervation

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Muscles of the Lower Limb

Introduction

The muscles of the lower limb are essential for stabilizing the pelvic girdle and facilitating movement such as standing, walking, and running. These muscles are organized into compartments and act on the hip, thigh, leg, and foot, each with specific actions, attachments, and innervation.

Muscles That Act on the Hip and Femur

Gluteal and Lateral Hip Muscles

The gluteal muscles are among the largest and most powerful in the body, responsible for movements at the hip joint. The gluteus maximus extends the thigh, while the gluteus medius and gluteus minimus abduct the thigh. The tensor fascia latae assists in flexion and abduction and stabilizes the knee via the iliotibial tract. Deep lateral rotators, such as the piriformis and obturator muscles, rotate the femur laterally.

Superficial pelvic and thigh muscles of right leg (anterior view), deep pelvic and thigh muscles of right leg (anterior view), and pelvic and thigh muscles of right leg (posterior view)

Iliopsoas: Flexes and laterally rotates the thigh; flexes the torso.
Gluteus maximus: Extends the thigh.
Gluteus medius/minimus: Abduct the thigh.
Tensor fascia latae: Flexes and abducts the thigh; stabilizes the knee.
Adductors (longus, brevis, magnus): Adduct and rotate the thigh; flex or extend depending on the muscle.
Pectineus: Adducts and flexes the femur at the hip.

Table: Muscles of the Hip and Thigh

Muscle Name	Primary Action	Origin	Insertion	Innervation
Iliopsoas	Flex, laterally rotate thigh; flex torso	Lumbar vertebrae, iliac fossa	Lesser trochanter	Femoral nerve
Gluteus maximus	Extend thigh	Dorsal ilium, sacrum, coccyx	Gluteal tuberosity, IT tract	Inferior gluteal nerve
Gluteus medius	Abduct thigh	Superior lateral ilium	Greater trochanter	Superior gluteal nerve
Adductor longus	Adduct, medially rotate, flex thigh	Pubis	Linea aspera	Obturator nerve
Pectineus	Adduct, flex, medially rotate thigh	Pectineal line of pubis	Lesser trochanter, linea aspera	Femoral nerve

Thigh Muscles That Act on the Femur, Tibia, and Fibula

Anterior, Medial, and Posterior Compartments

The thigh is divided into compartments by deep fascia. The anterior compartment contains the quadriceps femoris group, which extends the knee and stabilizes the joint. The medial compartment adducts the femur, while the posterior compartment (hamstrings) flexes the knee and extends the thigh.

Quadriceps femoris: Four muscles (rectus femoris, vastus lateralis, vastus medialis, vastus intermedius) that extend the knee.
Sartorius: Flexes, abducts, and laterally rotates the thigh; flexes the knee.
Hamstrings (biceps femoris, semitendinosus, semimembranosus): Flex the knee and extend the thigh.
Gracilis: Adducts the thigh and flexes the knee.

Superficial pelvic and thigh muscles of right leg (anterior view), deep pelvic and thigh muscles of right leg (anterior view), and pelvic and thigh muscles of right leg (posterior view)

Table: Thigh Muscles that Move the Femur, Tibia, and Fibula

Muscle Name	Primary Action	Origin	Insertion	Innervation
Gracilis	Adduct thigh, flex knee	Pubis, ischial ramus	Medial tibia	Obturator nerve
Sartorius	Flex, abduct, laterally rotate thigh; flex knee	ASIS	Medial proximal tibia	Femoral nerve
Rectus femoris	Extend knee, flex thigh	AIIS, acetabulum	Patella, tibial tuberosity	Femoral nerve
Biceps femoris	Extend, laterally rotate thigh; flex knee	Ischial tuberosity, femur	Fibular head, lateral tibia	Sciatic nerve

Muscles of the Lower Leg

Anterior, Lateral, and Posterior Compartments

The lower leg muscles are divided into three compartments. The anterior compartment dorsiflexes the foot and extends the toes. The lateral compartment everts and plantar flexes the foot. The posterior compartment (superficial and deep) plantar flexes the foot and flexes the toes.

Tibialis anterior: Dorsiflexes and inverts the foot.
Extensor digitorum longus: Extends toes, dorsiflexes foot.
Fibularis longus/brevis: Plantar flex and evert foot.
Gastrocnemius: Plantar flexes foot, flexes knee.
Soleus: Plantar flexes foot.
Flexor digitorum longus: Plantar flexes and inverts foot; flexes toes.
Flexor hallucis longus: Plantar flexes foot; flexes big toe.

Superficial and deep muscles of the right lower leg (anterior and posterior views)

Table: Muscles that Move the Feet and Toes

Muscle Name	Primary Action	Origin	Insertion	Innervation
Gastrocnemius	Plantar flex foot; flex knee	Femoral condyles	Posterior calcaneus	Tibial nerve
Soleus	Plantar flex foot	Tibia, fibula	Posterior calcaneus	Tibial nerve
Tibialis anterior	Dorsiflex, invert foot	Lateral tibia	Medial cuneiform, 1st metatarsal	Deep fibular nerve
Fibularis longus	Plantar flex, evert foot	Lateral fibula	1st metatarsal, medial cuneiform	Superficial fibular nerve

Intrinsic Muscles of the Foot

Structure and Function

The intrinsic muscles of the foot originate and insert within the foot, supporting the arch and enabling toe movements. The plantar aponeurosis provides principal support for the longitudinal arch. The dorsal group includes the extensor digitorum brevis, while the plantar group consists of four layers of muscles.

Muscles of the foot, including superficial, intermediate, and deep layers

Muscle Actions, Attachments, and Innervation

Muscle Actions

Each muscle has specific actions, such as flexion, extension, abduction, adduction, and rotation of the lower limb at various joints.
For example, the gastrocnemius plantar flexes the foot and flexes the knee, while the tibialis anterior dorsiflexes and inverts the foot.

Muscle Attachments

Muscle origins and insertions are critical for understanding their actions. For example, the rectus femoris originates from the anterior inferior iliac spine and inserts on the patella and tibial tuberosity.
The fibularis longus originates from the upper lateral fibula and inserts on the first metatarsal and medial cuneiform.

Muscle Innervation

Femoral nerve: Innervates iliopsoas, sartorius, quadriceps femoris, pectineus.
Obturator nerve: Innervates adductor longus, adductor brevis, adductor magnus, gracilis.
Tibial nerve: Innervates gastrocnemius, soleus, plantaris, tibialis posterior, flexor digitorum longus, flexor hallucis longus.
Sciatic nerve: Innervates biceps femoris, semitendinosus, semimembranosus.

Summary Table: Major Lower Limb Muscles, Actions, Attachments, and Innervation

Muscle	Action	Origin	Insertion	Nerve
Gluteus maximus	Extend thigh	Ilium, sacrum, coccyx	Gluteal tuberosity, IT tract	Inferior gluteal
Rectus femoris	Extend knee, flex thigh	AIIS	Patella, tibial tuberosity	Femoral
Biceps femoris	Flex knee, extend thigh	Ischial tuberosity, femur	Fibular head, lateral tibia	Sciatic
Gastrocnemius	Plantar flex foot, flex knee	Femoral condyles	Calcaneus	Tibial
Tibialis anterior	Dorsiflex, invert foot	Lateral tibia	Medial cuneiform, 1st metatarsal	Deep fibular

Key Concepts and Applications

Understanding muscle compartments and their innervation is essential for diagnosing nerve injuries and movement disorders.
Knowledge of muscle attachments helps explain the mechanics of movement and common injuries, such as strains and tears.
Precise terminology is required for describing muscle actions, especially in clinical and academic settings.

Additional info: The tables and images provided are derived from OpenStax Anatomy & Physiology, ensuring alignment with standard college-level curriculum.