Fascia and Muscles of the Leg Flashcards
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
NOTE:
- A fibulocalcaneus (peroneocalcaneus) interim muscle may be found with proximal attachment to the fibular head and distal attachment to the calcaneus
