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The back of the leg (calf) extends from the popliteal fossa above to the heel below.
It contains the superficial and deep posterior compartments, separated by the transverse intermuscular septum.
The main functions of these muscles:
Plantarflexion of ankle,
Flexion of toes,
Venous pumping action (“peripheral heart” effect).
Blood supply → posterior tibial and peroneal arteries.
Nerve supply → tibial nerve.
Lies between the skin and deep fascia.
Contains:
Small (short) saphenous vein,
Cutaneous nerves (sural, posterior cutaneous nerve of thigh, etc.),
Superficial lymphatics,
Variable fat, more abundant in the calf.
Fascia firmly adheres to skin, making subcutaneous infections or abscesses painful and localized.
Origin: Lateral end of dorsal venous arch + lateral marginal vein on dorsum of foot.
Course:
Passes behind the lateral malleolus.
Ascends lateral to tendo calcaneus, along midline of calf.
Pierces deep fascia in lower part of popliteal fossa.
Opens into the popliteal vein.
Drains: Lateral side of foot, heel, and back of leg.
Connections: Communicates with great saphenous vein and deep veins through perforators.
Accompanied by: Sural nerve along most of its course.
Origin: Medial end of dorsal venous arch + medial marginal vein of great toe.
Course:
Passes in front of the medial malleolus, ascends along medial leg and thigh.
Pierces cribriform fascia at saphenous opening to join femoral vein.
Tributaries: Medial marginal vein, superficial epigastric, circumflex iliac, external pudendal veins.
Valves: About 10–15, one always at saphenofemoral junction.
Communications: With small saphenous and deep veins via perforators (3 above ankle, 1 below knee, 1 at adductor canal).
Applied anatomy: Valve incompetence → varicose veins.
| Feature | Long (Great) Saphenous | Short (Small) Saphenous |
|---|---|---|
| Beginning | Medial end of dorsal venous arch | Lateral end of dorsal venous arch |
| Relation to malleolus | In front of medial malleolus | Behind lateral malleolus |
| Valves | 10–15 | 8–10 |
| Sensory nerve related | Saphenous nerve | Sural nerve |
| Termination | Femoral vein | Popliteal vein |
Sural nerve (L5, S1, S2):
Branch of tibial nerve in popliteal fossa.
Descends between gastrocnemius heads, joins peroneal communicating nerve, accompanies small saphenous vein.
Runs behind lateral malleolus to lateral foot and little toe.
Supplies: Skin of lower half of back of leg and lateral side of foot.
Posterior cutaneous nerve of thigh (S1–S3): Upper part of calf.
Lateral cutaneous nerve of calf (L4–S1): Upper two-thirds of lateral leg.
Medial calcanean branches (S1, S2): From tibial nerve → heel and medial sole.
Incision along lateral and medial borders of calf; reflect skin distally to heel.
Identify:
Small saphenous vein,
Sural nerve,
Posterior cutaneous nerve of thigh,
Lateral cutaneous nerve of calf,
Medial calcanean branches.
Observe relation of sural nerve with small saphenous vein.
Sural nerve neuroma: Painful swelling after injury or surgery.
Sural nerve graft: Commonly harvested — purely sensory, superficial, easily identifiable between tendo calcaneus and lateral malleolus.
Varicose veins: Due to valve incompetence of great or small saphenous veins or perforators.
Perforator valve failure: Allows reverse blood flow → venous stasis and ulcers.
Saphenous venesection: Great saphenous vein anterior to medial malleolus used for emergency infusion.
Deep vein thrombosis (DVT): Common post-surgical risk; swelling and pain in calf due to clot formation in deep veins.
A dense fibrous sheath surrounding the muscles of the leg.
Continuous above with the popliteal fascia, and below with the deep fascia of the foot.
Firmly attached to the subcutaneous border of the tibia and to the fibula.
Sends intermuscular septa that divide the leg into compartments: anterior, lateral, and posterior.
In the posterior region, the fascia is strong and thick, contributing to the muscle-pumping mechanism aiding venous return.
The posterior compartment is divided by a transverse intermuscular septum into:
Superficial group → gastrocnemius, soleus, plantaris.
Deep group → popliteus, flexor digitorum longus, tibialis posterior, flexor hallucis longus.
Boundaries:
Anteriorly: Tibia, fibula, interosseous membrane, and intermuscular septa.
Posteriorly: Deep fascia of the leg.
Nerve supply: Tibial nerve.
Arterial supply: Posterior tibial artery and peroneal artery.
A strong fibrous band extending from medial malleolus to the medial process of calcaneal tuberosity.
Converts grooves behind the medial malleolus into fibro-osseous tunnels for tendons and neurovascular structures.
Structures passing deep to flexor retinaculum (anterior → posterior):
👉 Mnemonic: “Tom, Dick, And Very Nervous Harry”
T → Tibialis posterior tendon
D → Flexor digitorum longus tendon
A → Posterior tibial artery
V → Venae comitantes
N → Tibial nerve
H → Flexor hallucis longus tendon
Each tendon is enclosed in a synovial sheath, and the artery and nerve are embedded in loose areolar tissue for gliding during ankle movement.
Make a vertical midline incision over the calf and reflect skin laterally and medially.
Identify and clean the deep fascia; note its strong attachment to the tibia.
Reflect fascia carefully to expose:
Superficial group of muscles (gastrocnemius, soleus, plantaris).
Beneath them lies the transverse intermuscular septum separating the deep group.
Trace the posterior tibial artery and tibial nerve between deep muscles.
At the medial ankle, dissect to show flexor retinaculum and identify the order of structures deep to it (Tom-Dick-And-Very-Nervous-Harry).
Tarsal Tunnel Syndrome:
Compression of tibial nerve under the flexor retinaculum.
Causes pain, tingling, or numbness over the sole and toes.
May result from swelling, ganglion, or varicosity.
Posterior Compartment Syndrome:
Increased pressure within deep fascia compresses posterior tibial vessels and nerve → ischemic pain and sensory loss on sole.
Tendo Calcaneus (Achilles) Strain or Rupture:
Sudden plantarflexion against resistance (e.g. jumping).
Leads to loss of heel lift during walking; surgical repair may be required.
Varicose Veins:
Failure of perforator valves in posterior compartment.
Common near the medial side of the calf.
Sural Nerve Graft:
Preferred for nerve reconstruction because it is long, superficial, and purely sensory.
The posterior compartment contains seven muscles, arranged in two groups:
Superficial group: Gastrocnemius, Soleus, Plantaris
Deep group: Popliteus, Flexor digitorum longus, Tibialis posterior, Flexor hallucis longus
All are supplied by the tibial nerve and participate mainly in plantar flexion of the foot and flexion of the toes.
Origin:
Medial head – above medial condyle of femur.
Lateral head – above lateral condyle of femur.
Insertion:
Both heads form a broad aponeurosis that merges with soleus tendon to form the tendo calcaneus (Achilles tendon) → inserted into posterior surface of calcaneum.
Nerve: Tibial nerve (S1, S2).
Action:
Powerful plantar flexor of foot.
Assists in flexion of knee.
Clinical note: Active during jumping and running; spasm causes the “calf cramp”.
Origin:
Posterior surface of head and upper third of fibula,
Soleal line and middle third of tibia,
Fibrous arch between them.
Insertion:
Joins gastrocnemius to form the tendo calcaneus.
Nerve: Tibial nerve (S1, S2).
Action:
Plantar flexion of foot.
Important for maintaining standing posture (“antigravity muscle”).
Note: Lacks action on knee joint (unlike gastrocnemius).
Origin: Inferior end of lateral supracondylar ridge of femur and knee capsule.
Insertion: Long thin tendon runs between gastrocnemius and soleus → joins tendo calcaneus or calcaneum.
Nerve: Tibial nerve (S1, S2).
Action: Weak plantar flexor; may assist in knee flexion.
Clinical note: Often absent; tendon harvested for grafting (e.g. hand reconstruction).
Formed by gastrocnemius, soleus, and plantaris.
Inserts on posterior surface of calcaneum.
Surrounded by paratenon (no true synovial sheath).
Bursa: A small retrocalcaneal bursa lies between tendon and calcaneum.
Function: Transmits powerful plantar-flexing force to foot.
Applied: Rupture causes loss of heel-rise and inability to stand on toes.
Origin: Lateral surface of lateral femoral condyle and lateral meniscus.
Insertion: Posterior surface of tibia above the soleal line.
Nerve: Tibial nerve (L4–S1).
Action:
Unlocks the knee by laterally rotating femur on tibia (or medially rotating tibia on femur when limb free).
Weakly flexes knee.
Clinical note: Its tendon lies intracapsular but extrasynovial in the knee joint.
Origin: Posterior surface of tibia below soleal line.
Insertion: Divides into four tendons → bases of distal phalanges of lateral four toes.
Nerve: Tibial nerve (L5–S2).
Action: Flexes lateral four toes; assists in plantar flexion and supports longitudinal arch.
Origin: Posterior surfaces of tibia, fibula, and interosseous membrane.
Insertion: Tuberosity of navicular, medial cuneiform, and bases of 2nd–4th metatarsals.
Nerve: Tibial nerve (L4, L5).
Action: Plantar flexes and inverts foot; main support of medial longitudinal arch.
Origin: Lower two-thirds of posterior surface of fibula and interosseous membrane.
Insertion: Base of distal phalanx of great toe.
Nerve: Tibial nerve (S2, S3).
Action: Flexes great toe; aids plantar flexion; maintains medial longitudinal arch.
Note: Its tendon grooves the posterior talus and sustentaculum tali of calcaneum.
Remove the superficial group to expose the deep layer beneath the transverse intermuscular septum.
Identify the popliteus in the upper part of the leg; below it lie the three long flexors (FDL, TP, FHL) from medial to lateral.
Trace the posterior tibial artery and tibial nerve between FDL and TP.
Expose the flexor retinaculum at the ankle and demonstrate the order of tendons (Tom, Dick, And Very Nervous Harry).
Rupture of Achilles tendon:
Sudden pain and gap above heel; patient cannot stand on toes.
Often occurs in middle-aged athletes (“tennis leg”).
Calcaneal bursitis:
Inflammation of retrocalcaneal bursa → pain on dorsiflexion or wearing tight shoes.
Tibial nerve injury:
Loss of plantar flexion and inversion; sensory loss over sole → calcaneovalgus deformity (dorsiflexed, everted foot).
Tarsal tunnel syndrome:
Compression of tibial nerve under flexor retinaculum → pain and paresthesia in sole.
Tendonitis of FHL or FDL:
Overuse in dancers and runners → pain behind medial malleolus.
Venous pump failure:
Weakness of calf muscles reduces venous return → predisposes to varicose veins and edema.
Origin: Terminal branch of the popliteal artery at the lower border of popliteus.
Course:
Passes deep to gastrocnemius and soleus between superficial and deep groups of posterior-leg muscles.
Runs with the tibial nerve (nerve crosses artery from medial → lateral).
Descends on tibialis posterior, accompanied by two venae comitantes.
At the ankle, it passes deep to the flexor retinaculum (between FDL and FHL tendons).
Divides into medial and lateral plantar arteries beneath the retinaculum.
Relations (from above downward):
Covered by gastrocnemius, soleus, and deep fascia.
Crossed superficially by sural nerve and small saphenous vein.
Branches:
Peroneal (fibular) artery — large lateral branch.
Circumflex fibular branch.
Nutrient artery to tibia.
Muscular branches.
Communicating branch with peroneal artery.
Medial and lateral plantar arteries (terminal branches).
Surface marking:
From midpoint between medial malleolus and Achilles tendon → to a point midway between medial malleolus and heel.
Pulse point:
Felt posterior to medial malleolus, halfway between malleolus and Achilles tendon.
Origin: From the posterior tibial artery about 2.5 cm below popliteus.
Course:
Descends along medial crest of fibula in the posterior compartment.
Lies deep to soleus and flexor hallucis longus.
Terminates behind the lateral malleolus, forming lateral calcaneal branches.
Branches:
Muscular branches to posterior and lateral compartments.
Nutrient artery to fibula.
Perforating branch: pierces interosseous membrane 5 cm above ankle to anastomose with anterior lateral malleolar artery.
Communicating branch with posterior tibial artery.
Lateral calcaneal branches to heel.
Function: Supplies lateral and posterior compartments of the leg, including peroneal muscles and FHL.
Applied: Major collateral vessel if posterior tibial artery occluded.
Origin: Larger terminal branch of the sciatic nerve in the lower third of the thigh (apex of popliteal fossa).
Course:
Descends through the popliteal fossa, then passes under tendinous arch of soleus.
Travels with posterior tibial artery on tibialis posterior — artery medial to nerve above, then crosses superficial to it.
At ankle → passes deep to flexor retinaculum, between FDL and FHL.
Divides into medial and lateral plantar nerves beneath retinaculum.
Branches:
Muscular:
To gastrocnemius (both heads), soleus, plantaris, popliteus, FDL, TP, FHL.
Cutaneous:
Medial calcanean branches to heel.
Articular:
To knee and ankle joints.
Terminal:
Medial and lateral plantar nerves to sole of foot.
Root value: L4 – S3.
Functions: Motor to posterior-leg and plantar muscles; sensory to sole of foot and heel.
Posterior tibial pulse:
Palpated behind the medial malleolus between tendo calcaneus and flexor retinaculum.
Absence → peripheral arterial disease or diabetic angiopathy.
Tarsal tunnel syndrome:
Compression of tibial nerve under flexor retinaculum.
Symptoms: Burning pain and tingling in sole, worse at night.
Tibial nerve injury:
Loss of plantar flexion and inversion; clawing of toes; anesthesia of sole → calcaneovalgus deformity.
Aneurysm or thrombosis of posterior tibial artery:
Produces swelling and pain behind medial malleolus; diminished dorsalis pedis pulse due to poor anastomosis.
Peroneal artery occlusion:
May compromise blood flow to lateral leg and heel; collateral flow via perforating branch preserves dorsalis pedis.
Deep vein thrombosis (DVT):
Clot formation in deep veins accompanying posterior tibial or peroneal arteries; causes pain, warmth, swelling in calf.
Structures under the Flexor Retinaculum (medial ankle):
👉 Mnemonic: “Talented Doctors Are Never Hungry”
T – Tibialis posterior
D – Flexor digitorum longus
A – Posterior tibial artery
N – Tibial nerve
H – Flexor hallucis longus
(These are arranged from anterior → posterior.)
Soleus acts as a “peripheral heart” by pumping venous blood upward during contraction.
Soleus works like the first gear of locomotion, while gastrocnemius acts as the second and third gears during walking or running.
Tendo calcaneus (Achilles tendon) is the strongest tendon in the human body.
All muscles of the back of the leg (calf) are supplied by the tibial nerve.
Posterior tibial artery pulse is palpated between the medial malleolus and the calcaneum deep to the flexor retinaculum.
1. A basketball player complains of sudden pain and inability to stand on tiptoe after a jump.
→ Diagnosis: Rupture of Tendo Calcaneus (Achilles tendon).
→ Result: Loss of plantar flexion and a palpable gap above heel.
2. A dancer develops severe pain posterior to the medial malleolus with tingling in the sole.
→ Cause: Tarsal Tunnel Syndrome — compression of tibial nerve under flexor retinaculum.
3. A patient with diabetes has absent posterior tibial pulse behind the medial malleolus.
→ Indicates: Peripheral arterial disease or diabetic angiopathy.
4. A soldier complains of calf pain and swelling after prolonged immobility.
→ Diagnosis: Deep Vein Thrombosis (DVT).
→ Pathology: Thrombosis in deep veins around posterior tibial or peroneal vessels.
5. An elderly woman complains of calf cramps during walking that subside at rest.
→ Diagnosis: Intermittent Claudication due to narrowing of posterior tibial artery.
6. A road accident crush injury to leg produces swelling, pain, and loss of plantar flexion.
→ Condition: Posterior compartment syndrome — compression of posterior tibial artery and nerve.
7. A tennis player reports pain over the back of heel from repetitive plantar flexion.
→ Condition: Achilles tendinitis — inflammation of tendon or its sheath.
8. A patient has pain and swelling over the heel from tight footwear.
→ Diagnosis: Calcaneal bursitis (retrocalcaneal bursa inflammation).
9. A popliteal artery aneurysm compresses its branches — which artery may maintain blood flow to the foot?
→ Answer: Peroneal artery via its perforating branch (collateral circulation).
10. A person sustains a deep laceration on the medial side of the ankle; foot becomes dorsiflexed and everted.
→ Structure injured: Tibial nerve → loss of plantar flexion and inversion.
11. A surgeon harvesting the sural nerve for grafting must avoid which accompanying structure?
→ Answer: Small saphenous vein.
12. A young athlete presents with persistent calf pain, numbness of heel, and weak plantar flexion.
→ Likely: Entrapment neuropathy of tibial nerve in posterior compartment.
13. A patient with chronic varicose veins develops ulcer near the medial malleolus.
→ Reason: Failure of perforator valves connecting great saphenous and deep veins.
14. Why can calf muscles act as a “peripheral heart”?
→ Because contraction of soleus and gastrocnemius compresses veins → aids venous return against gravity.
15. During knee surgery, injury to popliteus causes difficulty in initiating flexion. Why?
→ Popliteus unlocks the knee by lateral rotation of femur on tibia.
16. A fracture of the fibula near the lower end causes foot drop. Which artery remains intact?
→ Answer: Posterior tibial artery.
17. An X-ray shows fracture of the fibular neck with loss of dorsiflexion and eversion. Which nerve?
→ Answer: Common peroneal nerve. (Though not in posterior compartment, it lies close to lateral border of popliteal fossa.)
18. An embolus in the popliteal artery spares the foot circulation. How?
→ Collateral supply through peroneal artery and plantar anastomoses.
19. Pain radiating along the sole with sensory loss over heel after prolonged standing suggests?
→ Tibial nerve compression under flexor retinaculum.
20. A congenital shortening of Achilles tendon causes the child to walk on toes.
→ Condition: Talipes equinus.
Additional common applied points (for viva and MCQ linkage):
Soleus acts during standing; gastrocnemius during movement.
Tendo calcaneus rupture produces “sudden snapping sound” and positive Thompson’s test (no plantar flexion on calf squeeze).
Posterior tibial artery pulse is an important vascular examination site in diabetics.
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