Muscles of the Hip, Thigh, Leg, and Foot: Structure, Function, and Innervation

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Muscles Crossing the Hip and Knee Joints

Overview of Muscle Groups

Muscles crossing the hip and knee joints are organized into anterior, medial, and posterior groups. Each group is responsible for specific movements of the thigh and leg, and all are enclosed by the fascia lata, the deep fascia of the thigh.

Anterior muscles: Flex the femur at the hip and extend the leg at the knee (foreswing of walking).
Posterior muscles: Extend the thigh and flex the leg (backswing of walking).
Medial (adductor) muscles: Adduct the thigh and have no effect on the leg.

Movements at the Hip Joint

Muscles anchored to the pelvic girdle move the thigh at the hip joint, producing flexion, extension, abduction, adduction, circumduction, and rotation.

Thigh flexors: Pass in front of the hip joint and include Iliopsoas (iliacus and psoas major), Tensor fasciae latae, Rectus femoris, and are assisted by medial adductors and Sartorius.

Table of anterior and medial muscles of the thigh Diagram of anterior and medial muscles of the thigh and leg

Medial (Adductor) Muscles of the Thigh

Adductor Muscles and Their Functions

The medial compartment contains adductor muscles that medially rotate the thigh and are used in movements that press the thighs together. These muscles also tilt the pelvis during walking to balance the body’s weight.

Adductor magnus
Adductor longus
Adductor brevis
Pectineus
Gracilis

Table of medial compartment muscles of the thigh Diagram of adductor muscles of the thigh

Anterior Thigh Extensors

Quadriceps Femoris and Associated Muscles

The quadriceps femoris is the prime mover of leg extension and consists of four heads: Rectus femoris, Vastus lateralis, Vastus medialis, and Vastus intermedius. All insert into the quadriceps tendon, which attaches to the patella and then via the patellar ligament to the tibial tuberosity.

Tensor fascia lata: Steadies the leg, flexes, and abducts the thigh.
Quadriceps femoris: Powerful knee extensor used for climbing, running, and jumping.

Table of anterior compartment muscles of the thigh Diagram of anterior and medial muscles of the thigh and leg Diagram of quadriceps femoris muscles

Posterior Muscles of the Hip and Thigh

Gluteal Muscles and Lateral Rotators

The posterior group includes muscles for thigh extension, abduction, and lateral rotation.

Gluteus maximus: Major thigh extensor and lateral rotator.
Gluteus medius: Abducts and medially rotates thigh.
Gluteus minimus: Medially rotates thigh.
Piriformis, Obturator externus/internus, Gemellus: Lateral rotators of the thigh.

Table of posterior muscles of the hip and thigh Diagram of posterior muscles of the hip and thigh Diagram of gluteal and lateral rotator muscles

Hamstrings: Muscles of the Posterior Thigh

Structure and Function

The hamstrings are fleshy muscles of the posterior thigh that cross both the hip and knee joints. They are prime movers of thigh extension and knee flexion and are innervated by the sciatic nerve.

Biceps femoris
Semitendinosus
Semimembranosus

Table of hamstring muscles Diagram of hamstring muscles

Muscles of the Leg

Compartments and Movements

The deep fascia of the leg is continuous with the fascia lata and segregates the leg into anterior, lateral, and posterior compartments. These compartments contain muscles responsible for movements at the ankle (dorsiflexion and plantar flexion), intertarsal joints (inversion and eversion), and toes (flexion and extension).

Anterior Compartment Muscles

Muscles in the anterior compartment are primary toe extensors and ankle dorsiflexors.

Tibialis anterior
Extensor digitorum longus
Fibularis tertius
Extensor hallucis longus

Diagram of anterior compartment muscles of the leg Table of anterior compartment muscles of the leg Diagram of tibialis anterior muscle Diagram of extensor hallucis longus and fibularis tertius Diagram of extensor digitorum longus muscle

Lateral Compartment Muscles

Muscles in the lateral compartment produce plantar flexion and eversion of the foot and stabilize the lateral ankle and arch.

Fibularis longus
Fibularis brevis

Table of lateral compartment muscles of the leg Diagram of lateral compartment muscles of the leg Diagram of fibularis longus muscle Diagram of fibularis brevis muscle

Posterior Compartment Muscles

Muscles in the posterior compartment act to plantar flex the ankle and are innervated by the tibial nerve.

Superficial muscles: Gastrocnemius, Soleus (together called Triceps surae), Plantaris
Deep muscles: Popliteus, Flexor digitorum longus, Flexor hallucis longus, Tibialis posterior

Table of superficial posterior compartment muscles Diagram of superficial posterior compartment muscles Table of deep posterior compartment muscles Diagram of deep posterior compartment muscles

Intrinsic Muscles of the Foot

Structure and Function

Intrinsic muscles of the foot flex, extend, abduct, and adduct the toes, and support the arches of the foot. The plantar aspect contains four layers of muscles, each contributing to toe movement and arch support.

Dorsal muscle: Extensor digitorum brevis
Plantar muscles: Organized into four layers (superficial to deep)

Table of intrinsic muscles of the foot Diagram of first and second layers of plantar foot muscles Table of third and fourth layers of plantar foot muscles Diagram of third and fourth layers of plantar foot muscles

Summary Tables: Actions of Muscles Acting on the Thigh, Leg, and Foot

Summary of Muscle Actions

The following tables summarize the actions of muscles acting on the hip, knee, ankle, and toes, including their primary movements and innervation.

Muscle	Hip Flexion	Hip Extension	Adduction	Medial Rotation	Lateral Rotation	Knee Flexion	Knee Extension
Iliopsoas	x (PM)
Quadriceps femoris							x (PM)
Adductor magnus			x (PM)	x	x
Gluteus maximus		x (PM)			x (PM)
Hamstrings		x (PM)				x (PM)

Summary table of muscle actions at hip and knee

Muscle	Plantar Flexion	Dorsiflexion	Inversion	Eversion	Toe Flexion	Toe Extension
Tibialis anterior		x (PM)	x
Extensor digitorum longus		x		x		x (PM)
Fibularis longus	x			x
Gastrocnemius	x (PM)
Flexor hallucis longus	x				x (PM)

Summary table of muscle actions at ankle and toes

Compartmentalization of Thigh and Leg Muscles

Functional Anatomy

Muscles of the thigh and leg are organized into compartments, each with distinct functions and innervation.

Thigh: Anterior (extends leg), medial (adducts thigh), posterior (flexes leg and extends thigh)
Leg: Anterior (dorsiflexes foot, extends toes), lateral (everts foot), posterior (plantar flexes foot, flexes toes)

Diagram of muscle compartments of thigh and leg

Key Terms and Concepts

Prime mover (PM): The muscle primarily responsible for a specific movement.
Fascia lata: Deep fascia enclosing the thigh muscles.
Retinacula: Thickened fascia that holds tendons in place near joints.
Innervation: The nerve supply to a muscle, critical for its function.

Example: Walking

During walking, anterior muscles flex the hip and extend the knee during the foreswing, while posterior muscles extend the hip and flex the knee during the backswing. Medial muscles stabilize the pelvis and adduct the thigh to maintain balance.

Additional info:

The tables and diagrams provide a comprehensive overview of muscle origins, insertions, actions, and innervation, which are essential for understanding musculoskeletal function and clinical assessment in anatomy and physiology.