9.03 Bones and Muscles of the Leg/Foot Flashcards
What are the 2 major bones that make up the lower leg. Describe their locations
Describe the major function of each bone
The tibia Iocated medially and the fibulla located laterally.
- The tibia is the main weight bearing bone in the lower leg
- The fibula is mainly for muscle attachment and stabilisation of the ankle joint (it has no weight bearing function)
Label these parts on the anterior and posterior tibia
- condyles
- intercondylar eminence
- tibial tuberosity
- soleal line
- medial malleolus
- Epiphysis line
Label the following on the fibia
- head
- shaft
- borders - anterior, posterior and interosseus
- lateral malleolus
9 muscles attach to the fibula. How many of these insert and how many originate?
Only 1 attaches to the anterior border and it inserts
The others originate from it
There are 2 anterior borders of the tibia. Describe these and relate it to what is felt as the “shin”
The tibia is a triangular bone until the distal end (it has an anterior border anteriorly w/ surfaces projecting laterally & medially from it).
The anteromedial projection can be felt as the shin as it is subcutaneous the lateral surface is covered by muscle
(The posterior surface also enclosed in muscle)
How are the muscles of the lower leg arranged? What divides these structures?
The lower leg is divided into 3 compartments: anterior, lateral and posterior
They are separated by deep fascia (connective tissue) called the crural fascia
The muscles in the compartments are generally divided by their functions.
What movements are the muscles of each of the compartments responsible for?
Anterior: dorsiflexion and inversion
Lateral: eversion
Posterior: plantar flexion and inversion
What is special about the posterior compartment of the lower leg?
It is the largest compartment and is separated further into a superficial and a deep posterior compartment by the deep fascia
What is the effect of the 180 degree rotation of the lower limb relative to upper limb?
ie. during development the outgrowth of limb paddles is different (the upper limb rotates 90 degrees laterally while the lower limb rotates 90 degrees medially)
This basically means that the rotation of the upper limb means that the first digit (thumb) is in the lateral position while the rotation of the lower limb means the first digit (big toe) is medial.
The main effect is that the upper limb has flexors anteriorly and extensors posteriorly. The lower limb has flexors posteriorly and the extensors anteriorly.
Any muscle that goes across the medial malleolus will have what king of action?
Inversion
The deep fascia of the lower leg crual fascia is very thick and is continuous with a few structures, what are these?
- Fascia lata (fascia of the thigh) superiorly
- The periosteum of tibia anteriorly
- The intermuscular septa (deep)
- The ankle retinaculae inferiorly
What separates the anterior and posterior compartments of the lower leg?
The interosseus membrane between the tibia and fibula
What is the ankle retinaculum?
What is its function?
What are the main types?
A collection of strong obliquely oriented bands in the crural fascia in the ankle region.
It retains the tendons of the muscles that travel to/through the ankle holding them in position, stopping them from bowstringing and losing tension.
- 1 flexor
- 2 extensor
- 2 fibular
What is the other significance of these retinaculum?
Relate this to clinical significance
They create tarsal tunnels (ant, post) for the passage of other structures like nerves and vessels to pass through them
Clinically, they are compromised in:
- Compartment syndrome
- Tarsal tunnel syndrome
Label the retinaculum on the following diagrams
There are special structures of connective tissue in the lower limb that are unique to man.
What are these and what is thier major functions?
The Achilles tendon, plantar aponeurosis, ileotibial band (ITB) and the tensor fascia lata (TFL).
They are important for the two functions:
- Binds structures down
- Storage of elastic energy during the stance phase and is released in the swing phases during locomotion - elastic recoil
What are the [4] muscles that make up the anterior compartment of the lower leg?
Running from medial to lateral…
- Tibialis anterior
- Extensor hallucis longus (EHL)
- Extensor digitorum longus (EDL)
- Fibularis tertius
“Timothy Has (a Very Nasty) Dirty Toe”
What nerve supplies motor innervation to the muscles of the anterior compartment of the lower leg?
The deep fibular nerve (L4,5)
What are the actions of the muscles of the anterior compartment of the lower leg?
Describe how they cause these actions
Dorsiflexion and inversion
- Tibialis anterior runs across the front of the tibia and runs obliquely down the medial aspect of the ankle thus causing inversion (and dorsiflexion)
- Extensor hallicus longus attaches to the halix to pull it upwards
- It also crosses the medial malleolous to get to the big to so inverts the foot
- Extensor digitorum longus attaches to the four lateral toes to pull them upwards
- Fibularis tertius attaches to dorsum of the 5th metatarsum (base) pulling it up
What bone of the ankle does not recieve any muscle attachments? What is the significance of this?
They DON’T attach to the tarlus, bypass it and go beyond it. Thus contractions of them all increase a back force facilitating stability at the joint
The muscles all arise from the anterior borders of either the tibia or the fibula bone. What is the clinical significance of this?
Shin splints (tenoperiostitis)
Lots of activity on hard surfaces with pulling of the muscle at its periosteal attachemnt on these bones can lead to microtrauma
What is compartment syndrome?
The muscles are surrounded by ‘tight’ fascia, especially anteriorly.
If swelling occurs (due to injury causing leakage from facets, veins, arteries, synovium) causes compression of the neurovascular bundle occurs
What are the muscles of the lateral compartment of the lower leg?
Where do they arise from?
- Fibularis longus
- Fibularis brevis
They both arise from the lateral aspect of the fibula
What are the muscles of the superficial compartment of the posterior compartment of the lower leg?
- Gastrocnemius
- Plantaris
- Soleus
Where does the line of gravity pass through in the lower legs?
What is the implication of this?
The line of gravity of the lower limb passes in front of ankle joint thus these powerful muscles are required to resist force of gravity in order to prevent forward falling
Describe the gastronemus muscle
It is a power muscle
It is a 2 joint muscle with 2 heads. It doesn’t like to perform both actions on the two joints simultaneously hence it’s tendon (calcaneus tendon) is susceptible to tendinopathy - active insufficiency
Describe the soleus muscle
especially in terms of its function
- It attaches from the soleal line on the posterior aspect of the tibia.
- It lies deep to gastrocnemius
- It has a high concentration of slow twitch muscle and is antigravity (postural)
What is an important features of the soleus muscle?
Venous sinuses run in substance of soleneus muscle and are very important in venous return
Plantar flexion and dorsiflexion movements are carried out by soleus muscle and they also facilitate venous return
Describe the plantaris muscle
It is a small muscle with a thin belly coming from the lateral chondyl of femur and it blends into the calcaneus tendon of the gastrocnemus muscle merging with archiles - it has no functional role
What is the archilles tendon and where is it?
What forms the archilles tendon?
It is a large tendon at the back of the ankle
It is formed by the gastrocnemius calcaneal tendon together with soleus tendon
The Achilles tendon is prone to strain in dynamic plantar flexion (running)
What makes it more prone to this than the others?
The muscles from anterior and posterior aspect of the leg are protected by synovial sheaths as they pass around the malloleili
The archilles tendon does not have this synovial protection - instead it as a paratenon (non-synovial protective sheath of CT)
The Achilles tendon is prone to inflammation, why is this?
It is protected anteriorly and posteriorly by bursae
which are prone to irritation (bursitis is common and painful)
What are the [4] muscles that make up the deep layer of the posterior compartment of the lower leg?
- Popliteus
- Tibialis posterior
- Flexor digitorum longus
- Flexor hallucis longus
“Pick Tom Dick (and Very Naughty) Harry”
Describe the actions and relations of the flexor hallicus longus and flexor digitorum longus
Flexor hallicus longus starts of more laterally on the back of the leg and heads towards the medial side of the foot to the big toe
Flexor digitorum longus runs more medially down the back of the foot and heads towards the toes
(they essentially cross over)
Hallicus is deep to the digitorum
Describe the popliteal muscle?
It is a unique muscle that remains proximally
It sweeps from the lateral side on top of the femur medially to the tibia
It runs under the collateral lateral ligament, it laterally locates the femur and it unlocks the knee (has opposite actions to the other muscles in the compartment)
Describe the tarsal tunnel
A fibro-osseous tunnel beneath (created by) the flexor retinaculum on the medial side of the ankle.
What structures run through the tarsal tunnel?
- Tendons of Tibialis posterior, Flexor Digitorum Longus & Flexor Hallidus Longus with their synovial sheaths
- The posterior tibial artery and vena commitantes
- The tibial nerve (dividing into medial/ lateral plantar nerves)
What are the [2] muscles of the dorsum of the foot?
Describe them
- Extensor Hallicis Brevis
- Extensor Digitorum Brevis
They come across dorsum of the foot creating the fleshy acspect of it aiding (only a little) with extension of the toes (dorsiflexion) but overall they are not powerful muscles
What muscles make up the first (superficial most) layer of the sole of the foot?
What is their function as a group?
- Abductor Hallucis
- Flexor Digitorum Brevis
- Abductor Digiti Minimi
These are important for stabilising the foot during locomotor activites (stability but not locomotion actions itself)
What muscles make up layer 2 of the sole of the foot?
Describe them
- (the FDL & FHL tendons)
- They both start medially and sweep under the foot towards their destinations)
- The Lumbricals (4)
- Each located medial to their respective tendon of the flexor digitorum longus
- Flexor accessorius (quadratus plantae)
- Unique muscle to man: straightens the line of pull of FDL as it is acting on the lateral toes
What are the muscles that make up layer 3 of the sole of the foot? [3]
- Flexor hallucis brevis
- Adductor hallucis
- Flexor digiti minimi
What is the major function of the third layer of the muscles in the sole of the foot?
They are important in propulsive phase of big toe
What makes up layer 4 (the deepest layer) of the sole of the foot?
Describe their actions
Interossei muscles between the metatarsal
- 4 dorsal (bipennate)
- 3 plantar
Plantar are adductors (PAD)
Dorsal are abductors away (DAB)
Where is the rotational axis of the foot?
Through the middle of the second phalange
What is the plantar aponeurosis?
What is the function?
It is a strong layer of white fibrous tissue located beneath the skin on the sole of the foot.
It is between the calcaneus tendon and the metatarsal heads
It binds skin of foot for grip & protection and maintains longitudinal arches of foot
What is tenoperiostitis?
What two muscles are the most prone to this and why?
It is shin splints
- Tibialis anterior/posterior prone to tenoperiostitis
This is because they attach to bone and pulling on them in running movements causes inflammation
