Flashcards in MSK Session 12 Deck (107):
What is the function of the ankle joint in upright posture?
Bear all body weight as it transfers to foot
What is the clinical importance of the ankle joint?
Arterial pulses of limb can be examined here
Where do venous and lymph drainages undergo particular changes so that their low pressure systems can return fluid to the body?
How do arteries, motor nerves and tendons enter the foot?
How do veins, sensory nerves and lymphatics exit the foot?
What prevents bow-stringing of the long tendons of leg muscles at the ankle?
How does the foot support body weight?
Establishes broad base for bearing body weight
What two opposing functions does the foot have?
Supporting body weight and organ of locomotion
What features of the foot allow it to be an organ of locomotion?
Loose to permit movement but stable when moving
Permits movement on flat, sloping and uneven surfaces
Able to lift body weight during initiation of movement
What forms the ankle joint proper?
Articulation of tibia and fibula w/talus
How many articular surfaces are there in the ankle joint proper?
What are the articular surfaces of the ankle joint proper lined with?
What are key landmarks in distal superficial venous drainage of the lower limb?
Where do the tibia and fibula articulate with each other?
Most of their lengths
What is the proximal articulation of the tibia and fibula?
What type of joint is the proximal articulation of the tibia and fibula?
Plane type synovial
What is the intermediate articulation of the tibia and fibula?
What is the distal articulation of the tibia and fibula?
What type of joint is the distal articualtion of the tibia and fibula?
Which two ligaments tie the ends of the tibia and fibula together in the tibio-fibular syndesmosis?
Anterior and posterior tibio-fibular ligaments
Which ligament deepens the articulatory surfaces of the tibio-fibular syndesmosis?
What type of joint is the ankle joint proper?
Mortise and tenon
Rolling hinge synovial
Why is the ankle joint described as a mortise and tenon joint?
Leg bones form recess (mortise)
Superiorly rounded talus fills recess (tenon)
What allows changes between extremes of plantarflexion and dorsiflexion at the ankle joint?
Superiorly rounded talus allows rolling in a plane
Which are the joint stabilising surfaces of the ankle joint?
Posterior distal tibio-fibular ligament
Transverse tibio-fibular ligament
Which are the weight bearing surfaces of the ankle joint?
(Fibula takes ~17% so contributes to stability)
Which bones of the foot form the medial longitudinal arch?
Which bones of the foot form the lateral longitudinal arch?
4th + 5th metatarsals
Which bones of the foot form the transverse arch?
Tarsals and metatarsals
What strengthens the transverse arch of the foot?
Long tendon of leg muscles
Why must the segmented structure of the foot be arranged in an arch?
Can only weight bare if in an arch
How many arches are present in the foot at birth?
Why may the foot appear flat in children
Subcutaneous fat pad masks arches present
In which two direction are the arches of the foot arranged?
1 transverse medio-lateral
What type of attachments does the talus have?
Where is the long axis of the talus directed?
Forwards and medially
What is the significance of the direction of the long axis of the talus?
Tibia and fibular can roll over and direct weight in its deviated path
How is the dorsal aspect of the talus identified?
Superiorly convex medial and lateral edges
Central portion concave
How does the posterior articular surface (body) of the talus compare to the anterior articular surface (head)?
What are the three parts of the talus bone?
Head, neck and body
What does the plantar surface of the talus form?
Talo-calcaneal (sub-talar) joints
What is visible on the inferior view of the talus?
What type of joint is the subtalar joint?
What allows side to side motion of the foot?
3 parts of subtalar joint
How is the talus orientated in relation to the calcaneus?
Slightly obliquely on anterior surface
What separates the two articulations of the talus and calcaneus?
Tarsal canal (sinus tarsi)
What is the anterior talocalcaneal articulation?
Convex talus on concave calcaneus
What is the posterior talocalcaneal articulation?
Concave talus accommodates convex calcaneus
What allows us to walk on sloping/uneven ground by allowing the use of the sides of the feet?
Subtalar joint facilitating version and inversion
How far can the foot usually be everted?
How far can the foot usually be inverted?
Which surfaces articulate in dorsiflexion?
Anterior option of talar trochlea occupies and completely fills mortise
What is joint stability like in dorsiflexion?
Adjustments at what contribute to stability of ankle joint in extreme dorsiflexion when the malleoli spread?
What innervates dorsiflexion?
Fibular division of sciatic nerve (L4-5 same as for great toe)
Which muscles cause dorsiflexion?
Assistance from extensor digitorum longus and extensor hallucis longus
What articulates in plantar flexion?
Posterior portion of talar trochlea occupies mortise
What allows some rotation for AB/AD-duction?
Posterior talar trochlea not filling mortise
Why is dorsiflexion less stable than plantar flexion?
What is the innervation of plantar flexion?
Tibial division of sciatic (S1-2)
Which muscles cause plantar flexion?
Assistance from tibialis posterior, FHL and FDL
Which ligament is the strongest of the ankle joint?
Where is the deltoid ligament positioned?
Originates from apex of medial malleolus and fans downwards in triangular shape to tarsal bones
Where do the anterior fibres of the medial ligament stretch down to?
Where do the middle fibres of the medial ligament of the ankle joint stretch down to?
Describe the posterior fibres of the deltoid ligament.
Talo-tibial which pass backwards and laterally
What is the deep ligament of the ankle joint?
Fibres attached to medial malleolus and medial talus
Which fibres of the deltoid ligament is the deep ligament of the ankle joint related to?
What do the anterior and posterior fibres of the lateral ligament of the ankle join?
Lateral malleolus and talus
What do the intermediate fibres of the lateral ligament of the ankle join?
Lateral malleolus and calcaneus
Why does trauma to the ankle usually result in injury to both medial and lateral aspects of the joint?
Joint forms arming of bones and ligaments
What causes a Pott's fracture?
Excessive eversion of the foot w/abduction and external rotation
What is a Pott's fracture?
Bimalleolar ankle fractures
Describe the mechanism of injury in Pott's fracture.
Pull on medial ligament often causes avulsion of medial malleolus
Talus moves laterally
Lateral malleolus sheared off
What injury to the fibula is commonly caused in Pott's fracture?
# superior to tibio-fibular syndesmosis
What happens if the tibia is carried anteriorly in Pott's fracture?
Posterior margin of distal tibia is sheared off by talus
What type of bones are the tarsals?
What are the characteristics of the tarsals that classify them as short bones?
6 articular surfaces
What is the anterior talofibular ligament?
Flat, weak band that extends anteromedially from lateral malleolus to neck of talus
What is the posterior talofibular ligament?
Thick, strong band horizontal medially and posteriorly that passes from malleolar fossa to lateral tubercle of talus
Which ligament is a round cord that joins the lateral malleolus to lateral calcaneus?
What is the nerve supply to the ankle joint?
Derived from tibial nerve and deep fibular
What is the blood supply of the ankle joint?
Arteries derived from malleolar branches of the fibular, anterior and posterior tibial arteries
What limits dorsiflexion by the muscles in the anterior leg compartment?
Passive resistance of triceps surae to stretching
Tension in medial and lateral ligaments
How is the gait cycle split into two phases?
What are the three stages of the stance phase in the gait cycle?
What are the functions of gluteus maximus, quadriceps femoris and the muscles in the anterior compartment of the leg during heel-strike?
Gluteus maximus: decelerates lower limb
Quadriceps femoris: keeps leg extended at knee and hip
Anterior compartment: maintain ankle dorsiflexion
What is the function of quadriceps femoris in the support stage of the stance phase?
Keeps leg extended to accept body weight
What do the foot inverters and everters do in the support stage in the stance phase of the gait cycle?
What is the function of gluteus medius and tensor fascia lata in the support stage of the stance phase in the gait cycle?
Which muscles are involved in the toe-off stage of the stance phase?
Hamstrings extend hip
Quadriceps femoris maintain extended knee
Posterior leg plantarflexes ankle
Which muscles are involved in the swing phase of the gait cycle?
Anterior compartment of leg
What is the function of iliopsoas and refute femoris in the swing phase of the gait cycle?
Keep hip flexed and resist gravity
What is the function of quadriceps femoris in the swing phase of the gait cycle?
Extend knee to position foot for landing
What role do the muscles in the anterior compartment of the leg play in the swing phase of the gait cycle?
Maintain ankle dorsiflexion
What are the 5 stages of the gait cycle?
What causes Trendelenberg gait?
Lesion of superior gluteal nerve
Why does the pelvis drop on the side of the raised leg in a Trendelenberg gait?
Abductor muscles on opposite side of pelvis are paralysed
Describe the movements of the trunk in Trendelenberg gait.
Lurches to opposite side of pelvic drop then whips back but overcompensates
What is an antalgic gait?
When the patient spends less time on painful limb
How is an antalgic gait identified?
What causes foot drop?
Lesion of common/deep fibular nerve
What is observed in foot drop?
Foot dragged on floor
How do patients with foot drop compensate for their lost plantarflexion?
High stepparent gait
Why do guardsmen fall forwards when they faint?
Centre of gravity passes just anterior to ankle joint
What are the components of the deltoid ligament?
Anterior and posterior tibiotalar