Gross Anatomy-Muscles of Posterior Compartment Flashcards
Describe the Posterior Compartment and what does it contain
• Largest compartment
• Divided into superficial and deep compartments
o By transverse intermuscular septum
• 3 superficial and 4 deep muscles
• 3 superficial mm. collectively make up the triceps surae
o Generates majority of plantarflexion force
• Calcaneal tendon (Achilles tendon)
o Most powerful and thickest tendon in body
o Continuation of aponeurosis formed by gastrocnemius and soleus mm.
Describe the Gastrocnemius m and what muscle compartment is it in?
• Most superficial muscle
• Two-headed, two-joint muscle
• O: Lateral head – lateral aspect of lateral condyle of femur
Medial head – popliteal surface of femur; superior to medial condyle
** I:** Posterior surface of calcaneus via calcaneal tendon
A: Plantar flexion with extended knee; raises heel during walking; leg flexion
** N:** Tibial n. (S1, S2)
B: Popliteal a.
Posterior Compartment
What or how does the Gastrocnemius m function?
- Functions most effectively with extended knee
- Incapable of producing plantarflexion when knee is fully flexed
Describe the Solelus m and its location
• Deep to gastrocnemius
• “Workhorse” of plantarflexion
• Large, flat muscle
• Tendinous arch of soleus
o Continuous proximal attachment
o Shaped like an inverted U
o On posterior aspects of fibula and tibia
• Accessory soleus present 3% of the time
o Lies medial to calcaneal tendon
• O: Posterior aspect of head and superior ¼ of posterior surface of fibula; soleal line,
middle 1/3 of medial border of tibia
** I:** Posterior surface of calcaneus via calcaneal tendon
A: Plantarflexion independent of position of knee; steadies leg on foot
N: Tibial n. (S1, S2)
B: Popliteal and posterior tibial aa.
Explain how to test the Triceps Surae mm. of the Posterior Compartment of the leg.
• To test triceps surae m.:
o Plantarflex foot against resistance (standing on toes)
o Normally, tendons can be seen and palpated
o Tests integrity of tibial n.
Describe the Plantaris m.
• Short belly, long tendon
o Tendon often mistaken for a nerve
o “Freshman’s nerve”
• Absent 5-10%
• Highly variable in size and form
• O: Inferior end of lateral supracondylar line of femur; oblique popliteal l.
** I:** Posterior surface of calcaneus via calcaneal tendon
** A:** Weak plantarflexion
N: Tibial n. (S1, S2)
B: Popliteal and posterior tibial aa.
What is the Plantaris m considered and what is it’s tendon most often used for ?
• Considered an organ of proprioception for large plantarflexors
o Has high density of muscle spindles
• Tendon often used for grafting
Describe the Calcaneal Tendon Reflex and what nerves and muscle function does it test for.
• Also known as ankle-jerk reflex
• Calcaneal tendon struck with hammer
o Should result in plantarflexion of foot
• Tests S1-S1 (tibial n.)
o If S1 is damaged, reflex is virtually absent
• Tests function of gastrocnemius and soleus mm.
Explain how a Calcaneal Tendon Rupture occurs and what does it effect.
• Most severe acute muscle injury in leg
• Occurs in those who are poorly condition and have a history of calcaneal tendinitis
• Produces an audible “snap”
o During forceful push off (plantarflexion with knee extended)
• Followed immediately by sudden calf pain and sudden dorsiflexion of plantarflexed foot
o Bruising and lump appear in calf
• If tendon is completely ruptured, gap is palpable
• Results in inability to:
o Plantarflex against resistance
• Passive dorsiflexion will be excessive
• Ambulation is possible with laterally rotated limb
• Usually requires surgical intervention
Describe the Plantaris m and its location and action on the Posterior Compartment of teh leg.
• Thin, triangular muscle
• Forms inferior part of floor of popliteal fossa
• Belly emerges from joint capsule of knee
• O: Lateral surface of lateral condyle of femur and lateral meniscus
** I:** Posterior surface of tibia, superior to soleal line
A: Weak flexion of leg; unlocks knee by rotating femur 5 degrees on fixed tibia; medially
rotates tibia of unplanted limb
N: Tibial n. (L4, L5, S1)
B: Popliteal a.
What does the Plantaris m assist in flexion of the leg and support?
- Insignificant flexor of knee joint
- Assists PCL in preventing anterior displacement of femur on tibia
Describe the locationa and characteristics of the Flexor Hallicus Longus m (FHL)
• Powerful flexor of all joints of great toe
o Toe off
• Tendon passes posterior to medial malleolus
• Then runs between two sesamoid bones in tendons of flexor hallucis brevis m.
o Protect tendon
• O: Inferior 2/3 of posterior surface of fibula; inferior part of interosseous membrane
I: Base of distal phalanx of great toe
- *A:** Flexion of great toe at all joints; weak plantarflexion
- N:** Tibial n. (S2, S3)
- B**: Fibular a.
How is the FHL m tested?
• To test FHL:
o Distal phalanx of great toe flexed against resistance
o Normally, tendon can be seen and palpated plantar aspect of great toe
o Tests integrity of tibial n.
Describe the Flexor Digitorum Longus m (FDL) and it’s location
• Smaller than FHL
• Tendon crosses over TP superior to medial malleolus
• Tendon passes posterior to medial malleolus
• Then passes superficial to tendon of FHL in sole of foot
• Direction of pull realigned by quadratus plantae m.
• O: Medial part of posterior surface of tibia inferior to soleal line; by broad tendon to
fibula
** I:** Base of distal phalanges of lateral 4 digits
** A:** Flexion of lateral 4 digits; plantarflexion
** N:** Tibial n. (S2, S3)
** B: Posterior tibial a.**
How could the FDL m be tested?
• To test FDL:
o Distal phalanges of lateral 4 toes are flexed against resistance
o Normally, tendons can be seen and palpated
o Tests integrity of tibial n.
