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.
Describe the Tibialis Posterior m and its location.
• Deepest muscle in posterior compartment
• Between FHL and FDL
• Tendon passes immediately posterior to medial malleolus
• O: Interosseous membrane; posterior surface tibia inferior to soleal line; posterior
surface fibula
I: Tuberosity of navicular, cuneiform, cuboid, sustentaculum tali and bases of 2nd-4th
metatarsals
A: Plantarflexion and inversion
N: Tibial n. (S2, S3)
B: Posterior tibial a.
What is the Tibialis Posterior m synergist to, its primary role and how is it tested?
- Synergist to TA for inversion
- Primary role is to support medial longitudinal arch
• To test TP:
o Invert foot against resistance with foot slightly plantarflexed
o Normally, tendon can be seen and palpated posterior to medial malleolus
o Tests integrity of tibial n.
Explain the“Tom, Dick And Very Nervous Harry” reference
• Reference the relationship of the tendons of the mm. in the deep post. compartment (and neurovascular structures) to the medial malleolus
• From just post. (or closest to) the medial malleolus and working post:
o Tibialis Posterior m. “Tom”
o Flexor Digitorum Longus m. “Dick”
o Posterior Tibial a. “and”
o Posterior Tibial v. “very”
o Tibial n. “nervous”
o Flexor Hallucis Longus m. “Harry”
• REMEMBER - This only applies to the structures as they pass behind the medial malleolus not anywhere else!!!
What are the two main Arteries of the Vasculature of the Posterior Coompartment of the leg ?
o Posterior tibial a
**o Fibular a. **
Describe the Posterior tibial a. and its vasculature in the posterior compartment of the leg
o Posterior tibial a. – terminal branch of popliteal a
Runs in deep posterior compartment with tibial n.
Supplies knee, posterior leg, ankle
Fibular a.
Circumflex fibular a. –
• Participates in genicular anastomosis
Posterior tibial recurrent a. –
• Participates in genicular anastomosis
Muscular branches
Calcaneal and posterior medial malleolar branches
• Supply ankle and heel
Passes posterior to medial malleolus between FDL and posterior tibial v.
• One of four places to take a pulse
Terminates as:
• Medial and lateral plantar aa.
Describe the Fibular a of the posterior compartment of the leg
o Fibular a. – from posterior tibial a.
Perforating branches –
• Supply lateral compartment
Nutrient a. to fibula
Terminates as:
• Anterior and posterior lateral malleolar branches
• Lateral calcaneal branches
What are the two Veins in the Posterior Compartment of the leg and their location?
o Great saphenous v.
o Small saphenous v. –
Arises from lateral side of dorsal venous arch
Ascends posterior to lateral malleolus
Pierces deep fascia
Ascends between heads of gastrocnemius m.
Drains into popliteal v
