Muscles of the Lower Limb

 

Muscles of the Lower Limb: Complete Anatomy & Function

The lower limb muscles are crucial for movement, posture, and weight-bearing. They enable walking, running, climbing, jumping, and balance. These muscles are divided regionally into:

• Hip muscles

• Thigh muscles (anterior, posterior, medial compartments)

• Leg muscles (anterior, posterior, lateral compartments)

• Foot muscles (dorsal and plantar)

Let’s explore each group with origin, insertion, innervation, and function, along with clinical and functional significance.

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🧍‍♂️ I. HIP MUSCLES

1. Gluteal Muscles (Posterior Hip)

Muscle	Origin	Insertion	Innervation	Action
Gluteus Maximus	Ilium, sacrum, coccyx	Gluteal tuberosity, IT band	Inferior gluteal nerve	Hip extension, lateral rotation
Gluteus Medius	Outer surface of ilium	Greater trochanter	Superior gluteal nerve	Hip abduction, medial rotation
Gluteus Minimus	Outer surface of ilium (below)	Greater trochanter	Superior gluteal nerve	Hip abduction, medial rotation
Tensor Fascia Lata	ASIS, iliac crest	IT band	Superior gluteal nerve	Hip flexion, abduction, medial rotation

Clinical Note: Weakness in gluteus medius/minimus causes Trendelenburg gait.

2. Deep Lateral Rotators (Piriformis group)

Includes: Piriformis, Gemellus Superior/Inferior, Obturator Internus/Externus, Quadratus Femoris

Function: Lateral (external) rotation of the hip; stabilizes the femoral head.

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🦵 II. THIGH MUSCLES

A. Anterior Compartment (Extensors of Knee)

Muscle	Origin	Insertion	Innervation	Function
Iliopsoas (psoas + iliacus)	Lumbar spine + iliac fossa	Lesser trochanter	Femoral nerve + lumbar plexus	Strongest hip flexor
Sartorius	ASIS	Medial tibia (pes anserinus)	Femoral nerve	Hip flexion, abduction, lateral rotation, knee flexion
Quadriceps Femoris (Rectus femoris, Vastus lateralis, medialis, intermedius)	Rectus: AIIS, Vasti: femur	Tibial tuberosity via patellar ligament	Femoral nerve	Knee extension (rectus also flexes hip)

💡 Training relevance: Squats, lunges, and leg presses strengthen quadriceps.

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B. Medial Compartment (Hip Adductors)

Muscle	Origin	Insertion	Innervation	Function
Adductor Longus	Pubis	Linea aspera (femur)	Obturator nerve	Hip adduction, flexion
Adductor Brevis	Pubis	Linea aspera	Obturator nerve	Hip adduction
Adductor Magnus	Ischial tuberosity + pubis	Linea aspera + adductor tubercle	Obturator & sciatic nerves	Adduction, extension (hamstring part)
Gracilis	Pubis	Medial tibia (pes anserinus)	Obturator nerve	Adduction, knee flexion
Pectineus	Pubis	Pectineal line of femur	Femoral ± Obturator	Adduction, flexion

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C. Posterior Compartment (Hamstrings)

Muscle	Origin	Insertion	Innervation	Function
Biceps Femoris	Long head: ischial tuberosity; Short: linea aspera	Head of fibula	Sciatic nerve	Knee flexion, hip extension
Semitendinosus	Ischial tuberosity	Medial tibia (pes anserinus)	Sciatic nerve	Knee flexion, hip extension
Semimembranosus	Ischial tuberosity	Medial tibial condyle	Sciatic nerve	Knee flexion, hip extension

⚠️ Common Injury: Hamstring strains are frequent in sprinting.

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🦿 III. LEG MUSCLES (BELOW THE KNEE)

A. Anterior Compartment (Dorsiflexors)

Muscle	Action	Innervation
Tibialis Anterior	Dorsiflexes and inverts foot	Deep fibular nerve
Extensor Hallucis Longus	Extends big toe, dorsiflexes foot	Deep fibular nerve
Extensor Digitorum Longus	Extends toes 2–5, dorsiflexes foot	Deep fibular nerve
Fibularis Tertius	Dorsiflexion, eversion	Deep fibular nerve

🧠 Condition: Weak dorsiflexors → foot drop.

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B. Lateral Compartment (Everters)

Muscle	Action	Innervation
Fibularis Longus	Everts foot, supports arch	Superficial fibular nerve
Fibularis Brevis	Everts foot	Superficial fibular nerve

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C. Posterior Compartment (Plantarflexors)

Superficial Group (powerful plantarflexion):

Muscle	Insertion	Innervation	Action
Gastrocnemius	Calcaneus via Achilles	Tibial nerve	Plantarflexion, knee flexion
Soleus	Calcaneus (Achilles)	Tibial nerve	Plantarflexion only
Plantaris	Calcaneus	Tibial nerve	Weak plantarflexion

Deep Group (fine control):

Muscle	Function
Tibialis Posterior	Inverts, plantarflexes, arch support
Flexor Digitorum Longus	Flexes toes 2–5, plantarflexion
Flexor Hallucis Longus	Flexes big toe, plantarflexion
Popliteus	Unlocks knee (rotates tibia)

🔁 Mnemonic (for deep posterior): Tom, Dick And Nervous Harry → Tibialis Posterior, FDL, Artery (posterior tibial), Nerve (tibial), FHL

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🦶 IV. FOOT MUSCLES

A. Dorsal Foot (Extensors)

Muscle	Action	Innervation
Extensor Digitorum Brevis	Extends toes	Deep fibular nerve
Extensor Hallucis Brevis	Extends big toe	Deep fibular nerve

B. Plantar Foot (Intrinsic Muscles)

Organized into 4 layers, with functions like toe abduction/adduction, toe flexion, and maintaining arches.

Layer 1: Abductor hallucis, Abductor digiti minimi, Flexor digitorum brevis
Layer 2: Quadratus plantae, Lumbricals
Layer 3: Flexor hallucis brevis, Adductor hallucis, Flexor digiti minimi brevis
Layer 4: Dorsal and Plantar Interossei (abduct/adduct toes)

🦶 Function: Essential for balance, grip, and shock absorption during walking.

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⚕️ Common Injuries & Clinical Points

• Plantar fasciitis: Overuse injury of foot sole fascia

• IT band syndrome: Tight tensor fascia lata affecting lateral knee

• Shin splints: Irritation of tibialis anterior/periosteum

• Hamstring strain: From explosive sports movements

• Piriformis syndrome: Compression of sciatic nerve

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🏋️‍♂️ Functional Training Relevance

• Glute bridges, squats, lunges = strengthen hip/thigh muscles

• Heel raises, toe walks = activate calf and tibialis anterior

• Single-leg balance work = challenges foot intrinsics and stabilizers

• Stretching of hamstrings, calves, hip flexors aids injury prevention

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📌 Summary Table

Region	Key Muscles	Main Actions
Hip	Gluteals, deep rotators	Extension, abduction, rotation
Thigh	Quads, hamstrings, adductors	Knee extension/flexion, adduction
Leg	Tibialis, gastrocnemius, fibularis	Dorsi-/plantarflexion, eversion/inversion
Foot	Intrinsics (lumbricals, interossei)	Toe movement, arch support