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Flashcards in Fascia and Muscles of the Leg Deck (87):

Deep fascia of the leg

"Crural fascia"
- Continuous with the fascia lata of the thigh proximally


Attachments of crural fascia

o Patella
o Patellar ligament
o Tibial tuberosity
o Condyles of tibia
o Head of fibula


Crural fascia forms the ________ posteriorly

Popliteal fascia


Crural fasica receives fibers from 5 tendons

o Biceps femoris
o Sartorius
o Gracilis
o Semitendinosus
o Semimembranosus


Subcutaneous periosteum of the tibia

o Continuous with the deep fascia anteriorly
o Thicker proximally
o Forms retinacula of the ankle distally
o Serves as partial origin for: tibialis anterior and extensor digitorum longus


Deep surface of periosteum gives rise to

- Anterior intermuscular septa
- Posterior intermuscular septa
- Deep transverse fascia


Anterior and posterior intermuscular septa

NOTE: anterior and posterior intermuscular septa separate peroneus longus and brevis from each other and from muscles of the anterior and posterior crural compartments


Muscles of the anterior crural compartment

o Tibialis anterior
o Extensor hallucis longus
o Extensor hallucis capsularis
o Extensor digitorum longus
o Peroneus (fibularis) tertius


Muscles of the lateral crural compartment

o Peroneus (fibularis) longus
o Peroneus (fibularis) brevis


Muscles of the posterior crural compartment - superficial group

- Gastrocnemius
- Soleus
- Plantaris


Muscles of the posterior crural compartment - deep group

- Popliteus
- Flexor hallucis longus
- Flexor digitorum longus
- Tibialis posterior


Tibialis anterior origin

Four origins:
- Lateral condyle of tibia
- Lateral surface of the tibia
- Interosseous membrane
- Deep crural fascia


Tibialis anterior insertion

The thick muscle descends vertically to its insertion on the…
- Medial plantar surface of the medial cuneiform
- Base of first metatarsal


Nerve supply to tibialis anterior

Deep peroneal (fibular) nerve


Function of tibialis anterior

- Dorsiflexor and inverter of the ankle
- Also a supinator (adduction, inversion) of the intertarsal joints


Origin of extensor hallucis longus

Middle 2/3 of the anterior surface of the fibula (medial to the origin of the extensor digitorum longus)
- Also has an accessory origin from the interosseous membrane


Insertion of extensor hallucis longus

Base of distal phalanx of the first digit, with an additional slip of insertion into the base of the first metatarsal


Nerve supply to extensor hallucis longus

Deep peroneal (fibular) nerve


Function of extensor hallucis longus

Three functions:
- Extension of the first metatarsophalangeal joint
- Dorsiflexion of the ankle joint
- Supination at the intertarsal joints


Notes on extensor hallucis longus

Located just lateral to the tibialis anterior
- Distally, the anterior tibial vessels and deep peroneal nerve lie between it and the tibialis anterior
- Distal to the inferior extensor retinaculum, it passes from lateral to medial, superficial to these neurovascular structures


Extensor hallucis capsularis

Accessory muscle


Extensor hallucis capsularis origin

Arises from an extension of the extensor hallucis longus tendon


Extensor hallucis capsularis insertion

Passes distally to insert on the medial surface of the capsule of the first MPJ


Extensor hallucis capsularis function

To lift the capsule out of the joint to prevent the entrapment of the capsule


Extensor digitorum longus origin

Five origins:
- Lateral condyle of the tibia
- Head and upper ¾ of the anterior surface of the fibula
- Interosseous membrane
- Deep fascia
- Anterior intermuscular septum (between it and peroneus longus)


Extensor digitorum longus insertion

Extensor expansion of the 2nd, 3rd, 4th and 5th digits


Extensor digitorum longus nerve supply

Deep peroneal (fibular) nerve


Extensor digitorum longus function

Extension of MPJs of the four lateral digits
- Also dorsiflexes and everts the ankle
- Pronates (abduction and eversion) of the intertarsal joints
- Think “PEDAb”)


Extensor digitorum longus notes

Found lateral to the extensor hallucis longus on the lateral extreme of the anterior crural compartment


Peroneus (fibularis) tertius origin

Lower 1/3 of anterior surface of the fibula


Peroneus (fibularis) tertius insertion

Follows extensor digitorum longus to its insertion on the base of the 5th met


Peroneus (fibularis) tertius nerve supply

Deep peroneal (fibular) nerve


Peroneus (fibularis) tertius function

- Dorsiflexor and everter of the ankle
- Pronator of intertarsal joints


Peroneus (fibularis) tertius notes

Peroneus tertius is an inconstant muscle that can be considered to be part of the extensor digitorum longus


Lateral crural compartment muscles (again)

- Peroneus (fibularis) longus
- Peroneus (fibularis) brevis


Peroneus longus origin

Five origins:
- Head of fibula
- Upper 2/3 of body/lateral surface of fibula
- Lateral tibial condyle
- Crural fascia
- Both intermuscular septa


Peroneus longus insertion

Ends in a long tendon, which…
- Passes posterior to lateral malleolus with peroneus brevis
- Passes deep to the superior peroneal retinaculum
- Passes across calcaneus (distal to the peroneal trochlea and under the inferior peroneal retinaculum
- Passes on lateral then plantar side of cuboid (under long plantar lig.)

It then insertions onto…
- Lateral side of base of 1st metatarsal
- Lateral side of medial cuneiform
- Accessory insertion into the base of the second metatarsal


Peroneus longus innervation

Superficial peroneal (fibular) nerve


Peroneus longus function

- Plantar flexes and everts the ankle joint
- Pronates at the intertarsal joints


Peroneus longus notes

Most superficial muscle in the lateral compartment
- Common peroneal (fibular) nerve passes into the anterior compartment of the leg through an opening between its attachment to the fibular head and fibular body


Peroneus longus variation

Os peroneum
- There is sometimes a sesamoid bone in its tendon, posterior to the lateral malleolus on the cuboid bone

Additional muscle slips
- May be additional slips to base of 3rd, 4th or 5th metatarsal or to the adductor hallucis


Peroneus brevis origin

Three origins:
- Lower 2/3 of the body/lateral surface of the fibula
- Crural fascia
- Both intermuscular septa


Peroneus brevis insertion

Tendon passes posterior to the lateral malleolus, anterior to the tendon of the peroneus longus
- Inserts into tuberosity of the 5th metatarsal


Peroneus brevis nerve supply

Superficial peroneal (fibular) nerve


Peroneus brevis function

- Plantar flexor and evertor at the ankle
- Pronates intertarsal joints


Peroneus brevis notes

Found deep to the peroneus (fibularis) longus muscle


Variations in the lateral compartment

- Two peroneus (fibularis) muscles are sometimes fused
- Peroneus (fibularis) accessorius ay arise from fibular between longus and brevis - Its tendon joints the peroneus longus tendon
- Peroneus digiti quinti may exist as a separate muscle
- Peroneus quartus - common accessory muscle (10-15%), arises from the fibula between peroneus brevis and flexor hallucis longus and inserts on the peroneal trochlea of the calcaneus (peroneocalcaneus externum) or the tuberosity of the cuboid (peroneocuboideus)


Posterior crural compartment - superficial group

- Gastronemius
- Soleus
- Plantaris


Gastrocnemius origin

Medial head
- Proximal and posterior part of the medial condyle of the femur (posterior to the adductor tubercle)

Lateral head
- Depression on the lateral side of the lateral condyle of the femur

Both origins extend to adjacent areas of the femur and the knee joint capsule


Gastrocnemius insertion

Fibers of the two heads approach each other in the midline to join in a tendinous raphe which forms the aponeurosis of the muscle
- The aponeurosis tapers distally and joins with the tendon of the soleus muscle to form the tendo calcaneus
- Tendo calcaneus inserts into the central part of the posterior surface of the calcaneus


Gastrocnemius nerve supply

Tibial nerve


Gastrocnemius function

- Plantar flexor of the ankle
- Supinator (adduction and inversion) of the intertarsal joints
- Flexes at the ankle


Gastrocnemius notes

Most superficial muscle of the superficial group


Gastrocnemius variation

- Lateral head may be absent, rarely the entire muscle is absent
- Lateral head may contain a sesamoid known as the fabella


Soleus origin

Three origins:
- Posterior surface of the head and body of the fibula (soleal line)
- Middle 1/3 of the tibia
- Tendinous arch between tibia and fibula under which the popliteal vessels and tibial nerve pass


Soleus insertion

Tendo calcaneus into the calcaneus


Soleus innervation

Tibial nerve


Soleus function

Plantar flexor at the ankle


Soleus notes

- Lies deep to the gastrocnemius
- Because of their common insertion and actions, the soleus and gastrocnemius together are called the triceps surae


Soleus variation

There may be accessory heads of the soleus


Plantaris origin

Two origins:
- Lateral supracondylar line of the femur
- Oblique popliteal ligament


Plantaris insertion

Tendon runs along the medial border of the tendo calcaneus
- Inserts into medial side of posterior surface of the calcaneus
On occasion, the plantaris tendon joins the tendo calcaneus


Plantaris innervation

Tibial nerve


Plantaris function

Plantar flexor a the ankle and flexor at the knee


Plantaris notes

- Small inconstant muscle
- Tendon of plantaris is found between the gastrocnemius and soleus
- Absent in about 10% of cases


Deep group of posterior muscles

- Popliteus
- Tibialis posterior
- Flexor digitorum longus
- Flexor hallucis longus


Popliteus origin

Three origins:
- Groove on the lateral condyle of the femur
- Arcuate popliteal ligament
- Lateral meniscus


Popliteus insertion

Proximal to the soleal line on the body of the tibia


Popliteus nerve supply

Tibial nerve


Popliteus function

Flexor and rotator at the knee (unlocks the knee)
- With weight on the limb, it rotates the thigh laterally
- With no weight, it rotates the leg medially


Popliteus notes

Popliteus muscle is a thin triangular muscle that forms the inferior portion of the floor of the popliteal fossa


Popliteus variation

- May have an accessory head arising from the sesamoid bone of the gastrocnemius (fabella)
- A popliteus minor muscle may be present which attaches proximally to the femur and distally to the posterior ligament of the knee joint
- A peroneotibialis muscle may lie deep to the popliteus muscle (it attaches proximally to the head of the fibula and distally to the oblique line of the tibia)


Flexor hallucis longus origin

Three origins:
- Distal 2/3 of the posterior surface of the fibula
- Interosseous membrane
- Posterior intermuscular septum


Flexor hallucis longus insertion

Tendon passes first in a groove on the posterior surface of the lower end of the tibia, then over the posterior surface of the talus and the inferior surface of the sustentaculum tali. On the sole of the foot, it passes between the two heads of the flexor hallucis brevis to insert on the…
- Base of the terminal phalanx of the first digit


Flexor hallucis longus nerve supply

Tibial nerve


Flexor hallucis longus function

- Flexor of the interphalangeal joint of the first digit
- Plantar flexor of the ankle
- Supinator at the intertarsal joints


Flexor hallucis longus variation

- May have an accessory attachment to the flexor digitorum longus
- May be a flexor accessorius digitorum longus with origin from the fibula or tibia and insertion into the quadratus plantae or directly from the long flexor tendon


Flexor digitorum longus origin

Posterior surface, medial to the vertical line of the proximal 2/3 of the body of the tibia below the soleal line


Flexor digitorum longus insertion

Distally, its tendon passes posterior to the medial malleolus with the tendon of the tibialis posterior
- Passes superficially to the deltoid ligament and to the tendon of the flexor hallucis longus
- It is joined by the quadratus plantae and then divides into four tendons that are inserted into the bases of the distal phalanges of digits two, three, four and five


Flexor digitorum longus nerve supply

Tibial nerve


Flexor digitorum longus function

Muscle flexes distal interphalangeal joints, plantar flexes the ankle joint and supinates the intertarsal joints


Tibialis posterior origin

Three origins:
- Most of the posterior surface of the interosseous membrane
- Posterior surface of the tibia, lateral to the vertical line and below the soleal line
- Upper 2/3 of the medial surface of the fibula


Tibialis posterior insertion

Distally, its tendon lies in a groove with the flexor digitorum longus as it passes posterior to the medial malleolus
- Then passes deep to the flexor retinaculum, superficially to the deltoid ligament and deep to the plantar calcaneonavicular ligament
- Here the tendon contains a sesamoid bone
- Inserts into the tuberosity of the navicular with extensions to the sustentaculum tali, three cuneiforms, cuboid and bases of the 2nd, 3rd and 4th metatarsals


Tibialis posterior nerve supply

Tibial nerve


Tibialis posterior function

Supinator of the intertarsal joints and plantar flexor at the ankle


Tibialis posterior notes

Lies between the flexor hallucis longus and flexor digitorum longus


Fibulocalcaneus (peroneocalcaneus) interim muscle

- A fibulocalcaneus (peroneocalcaneus) interim muscle may be found with proximal attachment to the fibular head and distal attachment to the calcaneus