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The sole forms the inferior (plantar) surface of the foot — specialized for support, locomotion, and weight transmission.
Divided into medial, lateral, and central regions based on thickness of skin, fascia, and underlying muscles.
The skin, fascia, and arches together provide shock absorption and grip.
The region is supplied by medial and lateral plantar nerves and arteries, which are terminal branches of the tibial nerve and posterior tibial artery respectively.
Muscles in layers (superficial → deep):
Abductor hallucis, Flexor digitorum brevis, Abductor digiti minimi
Quadratus plantae, Lumbricals
Flexor hallucis brevis, Adductor hallucis, Flexor digiti minimi brevis
Plantar and dorsal interossei
Functions: Weight bearing, propulsion, protection, and balance.
Thick, hairless, and strongly bound to underlying fascia by fibrous septa.
Shows deep flexion creases at joints of toes.
Contains numerous sweat glands, making it moist and resilient.
No sebaceous glands → dryness in this area leads to cracked heels.
Nerve supply:
Medial plantar nerve → medial three and half toes.
Lateral plantar nerve → lateral one and half toes.
Sural nerve → lateral margin.
Saphenous nerve → medial border of foot up to ball of great toe.
Calcanean branches of tibial nerve → heel.
Clinical relevance:
Highly sensitive → protective reflex against injury.
Plantar reflex (Babinski’s sign): stroking sole → normal flexion of toes; dorsiflexion indicates pyramidal tract lesion.
The fasciae consist of superficial fascia and deep fascia (plantar aponeurosis).
Composition: Fibrofatty tissue containing fat lobules, veins, nerves, and sweat glands.
Fat acts as a shock absorber and insulator, especially at the heel and ball of the foot.
The fibrous septa anchor the skin to the plantar aponeurosis, preventing sliding during walking.
Clinical relevance:
Plantar abscesses are localized due to tight fibrous septa.
Heel pad atrophy in elderly reduces cushioning → heel pain.
Dense triangular sheet of deep fascia covering the central part of the sole.
Apex: attached posteriorly to medial process of calcaneal tuberosity.
Base: divides near the roots of toes into five slips, which enclose digital tendons.
Functions:
Protects underlying vessels, nerves, and muscles.
Maintains longitudinal arch of foot.
Provides firm grip on the ground.
Clinical importance: Plantar fasciitis — inflammation and microtears of aponeurosis → heel pain.
Place cadaver supine with sole upward.
Make a midline incision from heel to tip of middle toe, with two transverse cuts across toes and heel.
Reflect skin and superficial fascia carefully to expose:
Plantar vessels and nerves (cutaneous branches).
Plantar aponeurosis — thick fibrous structure in the center.
Note:
Fat pads under heel and heads of metatarsals.
Fibrous septa connecting skin to fascia.
Identify branches of medial and lateral plantar nerves supplying digital skin.
The deep fascia of the sole is thick centrally and thin on the sides.
In the central part, it is condensed to form the plantar aponeurosis; on medial and lateral sides, it covers the respective muscular compartments.
It acts as a protective layer and maintains the arches of the foot by keeping plantar structures firmly bound.
Shape: Strong, triangular fibrous sheet in the middle of the sole.
Apex (posterior end):
Attached to the medial process of calcaneal tuberosity and blends with tendo calcaneus.
Base (anterior margin):
Splits near the heads of metatarsals into five digital slips.
Each slip divides into superficial and deep layers:
Superficial part joins the skin at the base of toes.
Deep part divides into two laminae that enclose the flexor tendons, digital vessels, and nerves.
Medial and lateral borders:
Send vertical intermuscular septa separating the sole into three compartments:
Medial compartment: abductor hallucis and flexor hallucis brevis.
Lateral compartment: abductor digiti minimi and flexor digiti minimi brevis.
Central compartment: flexor digitorum brevis, tendons of long flexors, lumbricals, and vessels.
Functions:
Protects underlying muscles, vessels, and nerves.
Provides firm grip for weight-bearing.
Supports longitudinal arch of the foot.
Acts as an attachment for skin septa, limiting spread of infection.
Short, strong fibrous bands connecting the plantar plates of all metatarsophalangeal joints.
Situated along the heads of the metatarsals.
Bind together the anterior ends of metatarsal bones → maintain the transverse arch of foot.
Give attachment to fibrous digital sheaths of the toes.
Clinical note: These ligaments prevent splaying of forefoot during standing or walking.
Strong fibrous tunnels enclosing the flexor tendons on the plantar side of the toes.
Extend from the heads of metatarsals to the bases of distal phalanges.
Each sheath forms an osteofibrous canal along with the phalanges and plantar plates.
Contents (within sheath):
Flexor digitorum longus and flexor digitorum brevis tendons.
Each tendon is surrounded by a synovial sheath to minimize friction.
Function:
Prevent bow-stringing of tendons during toe flexion.
Provide stability and smooth movement of flexor tendons.
Clinical note:
Infection of these sheaths → tenosynovitis, causing swelling along the affected toe.
Spread may extend to mid-palmar space in severe cases.
Plantar Fasciitis:
Inflammation and micro-tearing of plantar aponeurosis due to overuse or tight calf muscles.
Causes severe heel pain (especially on first step in morning).
Calcaneal Spur:
Bony outgrowth from the calcaneal tuberosity where aponeurosis attaches.
Often accompanies chronic plantar fasciitis.
Plantar Abscess:
Deep infection limited by tight fibrous septa → swelling is tense and very painful.
Incision must follow the line of septa to avoid damaging neurovascular bundles.
Rupture of Plantar Aponeurosis:
Sudden overstretching (e.g., jumping) may cause tearing → localized pain and loss of arch support.
Flat Foot (Pes planus):
Weakening of plantar aponeurosis and ligaments → collapse of medial longitudinal arch.
Diabetic Ulcers:
Common over pressure areas of sole due to loss of protective sensation and poor vascularity.
The sole contains 20 muscles arranged in four layers.
All are supplied by branches of the medial and lateral plantar nerves (terminal branches of the tibial nerve).
Muscles:
Abductor hallucis – from medial calcaneal tuberosity → base of proximal phalanx of great toe.
Nerve: Medial plantar nerve.
Action: Abducts and flexes great toe.
Flexor digitorum brevis – from calcaneal tuberosity → four tendons into middle phalanges of lateral four toes.
Nerve: Medial plantar nerve.
Action: Flexes lateral four toes at PIP joints.
Abductor digiti minimi – from calcaneal tuberosity → base of proximal phalanx of fifth toe.
Nerve: Lateral plantar nerve.
Action: Abducts and flexes little toe.
Muscles and tendons present:
Flexor digitorum longus (from posterior leg) – divides into four tendons → distal phalanges of lateral four toes.
Flexor digitorum accessorius (Quadratus plantae) – two heads from calcaneum → tendon of FDL.
Nerve: Lateral plantar nerve.
Action: Straightens the oblique pull of FDL.
Lumbricals (four small muscles) – arise from tendons of FDL.
Nerve:
1st lumbrical → Medial plantar nerve.
Remaining three → Lateral plantar nerve.
Action: Flex MTP joints and extend IP joints.
Flexor hallucis longus tendon (from leg) – runs medial to FDL; gives tendinous slip to it.
Muscles:
Flexor hallucis brevis – from cuboid and lateral cuneiform → medial and lateral sides of base of proximal phalanx of great toe.
Nerve: Medial plantar nerve.
Action: Flexes proximal phalanx of great toe.
Adductor hallucis – two heads:
Oblique head: from bases of 2nd–4th metatarsals and sheath of peroneus longus.
Transverse head: from plantar ligaments of lateral three MTP joints.
Insertion: Lateral side of base of proximal phalanx of great toe.
Nerve: Deep branch of lateral plantar nerve.
Action: Adducts great toe, maintains transverse arch.
Flexor digiti minimi brevis – from base of 5th metatarsal → base of proximal phalanx of little toe.
Nerve: Superficial branch of lateral plantar nerve.
Action: Flexes proximal phalanx of little toe.
Muscles:
Plantar interossei (3) – unipennate; arise from medial sides of 3rd–5th metatarsals.
Action: Adduct toes (PAD – plantar adduct).
Nerve: Deep branch of lateral plantar nerve.
Dorsal interossei (4) – bipennate; arise from adjacent sides of metatarsals.
Action: Abduct toes (DAB – dorsal abduct).
Nerve: Deep branch of lateral plantar nerve.
Also present:
Tendons of peroneus longus (crossing obliquely to medial cuneiform and 1st metatarsal).
Tibialis posterior insertion slip to medial cuneiform and navicular.
1. Medial Plantar Artery
Smaller terminal branch of posterior tibial artery.
Lies along medial border between abductor hallucis and flexor digitorum brevis.
Branches: Cutaneous, muscular, and 3 small superficial digital arteries joining plantar arch.
2. Lateral Plantar Artery
Larger branch; crosses sole to 5th metatarsal → curves medially to form plantar arch, completed by dorsalis pedis.
Branches:
4 plantar metatarsal arteries → divide into plantar digital arteries for adjacent sides of toes.
A branch to lateral side of little toe.
Calcaneal and anastomotic branches.
3. Medial Plantar Nerve (L4–S1)
Larger terminal branch of tibial nerve.
Between abductor hallucis and flexor digitorum brevis.
Supplies:
Muscles: Abductor hallucis, Flexor digitorum brevis, Flexor hallucis brevis, First lumbrical.
Skin: Medial 3½ toes.
4. Lateral Plantar Nerve (S1–S3)
Smaller terminal branch of tibial nerve.
Runs obliquely to 5th metatarsal between 1st and 2nd layers.
Divides into:
Superficial branch: to flexor digiti minimi brevis and skin of 1½ lateral toes.
Deep branch: accompanies plantar arch, supplies interossei, adductor hallucis, and 3 lateral lumbricals.
Morton’s Neuroma:
Painful thickening of plantar digital nerve (usually between 3rd and 4th metatarsals) due to compression by transverse metatarsal ligament.
Nerve Entrapment:
Medial plantar nerve entrapment → pain along medial sole (“Jogger’s foot”).
Lateral plantar nerve entrapment → pain in lateral sole and toes.
Plantar Fascial Conditions:
Plantar fasciitis and calcaneal spur cause heel pain radiating to sole.
Diabetic Neuropathy:
Loss of sensation on sole → trophic ulcers at pressure points.
Loss of Arches:
Weakening of plantar ligaments or muscles leads to flat foot (pes planus).
Origin:
Smaller terminal branch of the posterior tibial artery.
Course:
Runs forward along the medial border of the foot, between abductor hallucis and flexor digitorum brevis.
Termination:
Ends by dividing into several superficial digital branches that anastomose with plantar metatarsal arteries from the plantar arch.
Branches:
Cutaneous branches – to skin of medial sole.
Muscular branches – to abductor hallucis and flexor digitorum brevis.
Three superficial digital branches – join the first, second, and third plantar metatarsal arteries.
Functional note:
Supplies medial part of sole and medial 3½ toes through its branches.
Origin:
Larger terminal branch of the posterior tibial artery.
Course:
Runs obliquely across the sole to the base of the 5th metatarsal, where it gives a superficial branch and continues medially as the plantar arch.
Branches:
Muscular branches – to adjacent muscles.
Cutaneous branches – to skin and fascia of lateral sole.
Anastomotic branches – connect with arteries on the dorsum of foot.
Calcanean branch – occasionally to heel region.
Functional note:
Chief vessel forming the plantar arch and supplying the greater part of the sole.
Formation:
Formed by the continuation of the lateral plantar artery after giving its superficial branch.
Completed on the medial side by the deep plantar branch of the dorsalis pedis artery.
Course:
Extends from the base of the 5th metatarsal to the proximal part of the 1st intermetatarsal space.
Lies between the third and fourth layers of the sole.
Accompanied by venae comitantes and the deep branch of the lateral plantar nerve in its concavity.
Branches:
Four plantar metatarsal arteries, one in each intermetatarsal space → divide into plantar digital arteries for adjacent sides of toes.
First plantar metatarsal artery also gives a branch to the medial side of great toe.
Lateral side of little toe gets a direct branch from the lateral plantar artery.
Function:
Principal arterial network of the sole ensuring rich collateral circulation with the dorsalis pedis artery.
Morton’s Neuroma:
Painful thickening (neuroma) of the plantar digital nerve, usually between 3rd and 4th metatarsals.
Produces sharp burning pain during walking.
Ischemic Pain of Sole:
Spasm or occlusion of plantar arteries causes cramp-like pain (common in diabetic and atherosclerotic patients).
Plantar Hematoma:
Injury to plantar vessels may lead to deep hematoma due to tight fascia, producing severe pressure and pain.
Vascular Insufficiency:
In diabetes, diminished perfusion of plantar arteries → delayed healing and ulceration over metatarsal heads.
The sole of the foot is specialized for support, protection, and locomotion.
The skin is thick, hairless, and firmly anchored to deep fascia by fibrous septa.
The superficial fascia is fibrofatty and acts as a shock absorber.
The deep fascia is thickened centrally as the plantar aponeurosis, providing protection and maintaining the longitudinal arch.
The sole is divided into three compartments by septa from the aponeurosis: medial, lateral, and central.
Muscles of the sole (20 total) are arranged in four layers and supplied by medial and lateral plantar nerves.
Medial plantar nerve = equivalent to median nerve of hand (supplies 4 muscles and 3½ toes).
Lateral plantar nerve = equivalent to ulnar nerve of hand (supplies 14 muscles and 1½ toes).
Plantar arteries (medial and lateral plantar) are terminal branches of the posterior tibial artery.
The lateral plantar artery forms the plantar arch with dorsalis pedis artery.
Tendons crossing sole:
Flexor hallucis longus → to great toe.
Flexor digitorum longus → to lateral four toes.
They are connected by a tendinous slip.
Peroneus longus tendon runs obliquely across the sole to maintain the transverse arch.
Abductor hallucis and abductor digiti minimi maintain the medial and lateral longitudinal arches respectively.
Plantar interossei (PAD) adduct toes; Dorsal interossei (DAB) abduct toes.
Plantar aponeurosis prevents over-stretching of the arch during weight bearing.
Pulse of posterior tibial artery can be felt midway between medial malleolus and heel.
The plantar reflex (L5, S1) tests integrity of corticospinal tract.
Foot drop results from paralysis of dorsiflexors (anterior compartment); claw toes from paralysis of intrinsic muscles of sole.
Flat foot (pes planus) results from weakening of plantar aponeurosis, ligaments, and intrinsic muscles.
Morton’s neuroma involves digital nerve in 3rd intermetatarsal space due to chronic compression.
Plantar Fasciitis — Overuse inflammation of plantar aponeurosis → heel pain, worse on first morning steps.
Calcaneal Spur — Chronic traction at calcaneal tuberosity causes bony spur formation → point tenderness on heel.
Plantar Abscess — Deep infection limited by tight septa → swelling localized but extremely painful.
Morton’s Neuroma — Fibrosis around digital nerve between 3rd and 4th metatarsals → burning pain on walking.
Jogger’s Foot — Entrapment of medial plantar nerve under abductor hallucis → medial sole pain.
Baxter’s Neuropathy — Entrapment of first branch of lateral plantar nerve → pain near heel mimicking plantar fasciitis.
Diabetic Ulcer (Plantar) — Pressure sores due to neuropathy and ischemia, especially under metatarsal heads.
Flat Foot (Pes Planus) — Collapse of medial longitudinal arch due to weak ligaments or muscle fatigue.
Pes Cavus (High Arch) — Exaggerated arch due to overactive tibialis posterior or contracture of plantar fascia.
Rupture of Plantar Aponeurosis — Sudden jump or sprint causes tearing → acute pain and flattening of arch.
Tarsal Tunnel Syndrome — Compression of tibial nerve beneath flexor retinaculum → radiating sole pain.
Claw Toes — Paralysis of lumbricals and interossei → hyperextension at MTP joints, flexion at IP joints.
Hallux Valgus — Deviation of great toe laterally, compressing medial plantar digital nerves.
Hallux Rigidus — Degenerative arthritis of first MTP joint → restricted great toe movement.
Plantar Fibromatosis (Ledderhose Disease) — Fibrosis in plantar fascia → nodular thickening, painful lumps.
Metatarsalgia — Pain under metatarsal heads due to inflamed digital nerves or collapsed transverse arch.
Foreign Body in Sole — Difficult to remove due to dense fascia; infection easily localized by septa.
Gangrene of Toes — Arterial insufficiency from diabetes or peripheral vascular disease → tissue necrosis.
Venous Congestion of Sole — Prolonged standing causes venous stasis → throbbing pain and swelling.
Posterior Tibial Artery Occlusion — Loss of plantar pulses; ischemia causes pain and coldness in sole.
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