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WEEK 26:
how do we walk?
| Question | Answer |
|---|---|
| gait cycle | time interval between two successive occurrences of one a repetitive events of walking (right foot to right foot) |
| where is the body's centre of mass when walking | roughly between hip joints (with CoM vertical displacement during walking kept generally minimal) |
| phases in walking gait (2) | stance phase (foot on ground) and swing phase (foot in air) |
| average duration of stance phase | 60% |
| average duration of swing phase | 40% |
| difference between pathological gait and normal gait | in normal gait the right and left sides are similar but in pathological gait there is a difference between right and left |
| phases of gait cycle (7) | heel strike (initial contact), loading response (foot flat), midstance, terminal stance (heel off), preswing (toe off), initial and midswing, and terminal swing |
| lower limb contains | 31.5 separate bones and 52 separately named muscles |
| cyclic nature of muscle contraction during walking drives | muscle pump that brings venous blood towards the heart |
| in the lower limb what enables movement | three main joint/ muscle complexes (hip knee and ankle/foot) |
| hip joint | ball and socket synovial joint which is moved and stabilised by 21 separate muscles |
| movement of hip joint | flexion, extension, abduction, adduction, internal rotation, and external rotation |
| knee joint type joint | hinge synovial joint |
| knee joint movement are guided by | menisci and strong collateral and cruciate ligaments |
| knee joint is stabilised and moved by | 14 muscles, some being bi-articular (crossing both hip and knee, knee and ankle) |
| talocrural joint (foot-ankle joint) | mortise and tenon joint (fibula/tibia from mortise, talus forms the tenon) |
| clinical importance of the talocrural joint | supports load of body and supports achilles tendon |
| what two things come together to form the longest tendon in the body | long head of bi-articular gastrocnemius and mono-articular soleus |
| function of foot-ankle complex | assist power transfer from largest muscles to the ground for propulsion |
| foot ankle complex is stabilised and moved by | 33 different muscles on each side |
| strongest muscles in the foot-ankle complex | plantar flexors |
| which muscles use the calcaneus as a lever | soleus/ gastrocnemius (triceps surae) |
| which muscles provide additional support for ankle foot complex (3) | tibialis anterior, tibialis posterior, and fibularis longus |
| due to the attachment sites of the tendons of the additional muscles, they function as | stirrup for foot - ankle |
| foot consists of | 30 bones linked together by synovial joints help tightly apposed by ligaments (making an arched structure) and is further stabilised by strong ligaments and palntar fascia and smaller internal foot muscles |
| all the structures of the foot form | a spring which is loaded when the foot (rolls) on the ground upon contact and released at toe off |
| what happens when load is applied onto the foot | each of the joints gives a little, which leads to an observable but not dramatic deformation which is reversed by unloading |
| arch-spring and windlass mechanisms | describe functional behaviour of arch one through elasticity of arch spanning tissues and other through rigidity |
| when you walk the foot doesnt hit the ground flat it | rolls in a controlled way to absorb shock, distribute weight, and push forward efficiently |
| first point of contact to ground | heel - body weight starts loading onto the foot and the foot is slightly supinated (rigid) |
| after heel contacts ground where does the pressure shift | to heel (lateral border of foot) |
| why does pressure shift to the heel (lateral border of foot) after heel contacts ground | keeps foot stable initially and prevents collapse too early |
| explain midstance | weight shifts from heel (lateral border of foot) to medial arch and foot becomes more pronated (flexible) - medial arch acts like a spring and compressed slightly to absorb shock from body weight |
| explain push off (toe off) | pressure shifted from medial arch to hallux because the big toe is the strongest push off point and helps propel body forward |
| explain the pressure shifts and transfers in the walking gait cycle | heel -> lateral foot -> medial arch -> big toe |
| define heel strike (initial contact) | heel touches ground and LANDS, first (start of cycle) |
| define loading response (foot flat) | whole foot comes down and body weight transfers onto that leg (shock absorption phase) |
| define midstance | body weight is directly over the foot and other leg is swinging forward (balance phase) |
| define terminal stance (heel off) | heel lifts off ground and weight moves forward towards toes (preparing to push off) |
| define preswing (toe off) | toes push off ground, foot leaves the floor (push off phase) |
| which parts of the gait/ walking cycle are stance phase (5) | heel string, loading response, midstance, terminal stance, and preswing (toe-off) |
| define initial and mid-swing | leg lifts and moves forward and knee bends to clear ground (prevents tripping) |
| define terminal swing | leg straightens and prepares for next heel strike (reset for next step) |
| support phases include | double support (10%- both feet on ground and happens twice in cycle) and single support (40%- one foot on group other is swining) |
| basic summary of what happens during gait/ walking cycle | heel -> flat -> over -> off -> toe -> swing -> land |
| foot drop is caused by | damaged common fibular nerve injury |
| weak calf muscles lead to | poor push off (toe off) |
| hip abductor weakness leads to | instability during midstance |
| what is the loading phase | occurs after heel contact and refers to when your heel first hits the ground until the other foot lifts off (both feet are on the ground - double support phase) |
| during loading phase it is described as eccentric load which means | muscle is active while lengthening, so instead of moving you, muscles are controlling and slowing movement |
| during loading phase, what occurs | ankle dorsiflexors stop foot from slapping down, knee extensors (quadriceps) control knee bending, and hip abductors stabilise pelvis |
| body weight is where during loading phase and gait/ walking cycle | medial to hip joint |
| what would happen without muscles making the weight medial to hip joint during walking | pelvis would drop on the opposite side (swing side) |
| Trendelenburg sign | occurs when hip abductors are weak leading to pelvis drop on opposite side and patient would lean to compensate |
| important hip abductor muscles (3) | gluteus medius, gluteus minimus, tensor fascia latae (TFL) |
| what is mid-stance phase | from onset of single limb support to when body weight is over forefoot where tibia moves forward on talus due to momentum and hi abductors still active to prevent pelvis tilt |
| during midstance phase which strap muscles are included | semitendinosus, gracilis, and sartorius which all insert into the pes anserinus (line of gravity) to form an inverted tripod that allows for corrective movement during stance phase |
| during mid-stance phase, plantar flexors change from | eccentric to concentric load |
| difference between eccentric and concentric load | eccentric is lengthening but concentric is shortening |
| what is terminal stance phase | between moment weight is on forefoot to heel contact of the other limb (beginning of the second double limb phase) where plantar flexors maximally active concentrically (propulsion) where windlass mechanism will occur and hip abductors still active |
| what is preswing phase | covers second double limb phase from heel contact of swinging contralateral limb to toe off of stance limb where dorsiflexors (extensors of foot) active so foot can move freely and does not catch on ground |
| dorsiflexors (extensors of foot) included in preswing phase (3) | tibialis anterior, extensor hallucis, and extensor digitorum longus |
| what is initial swing/ midswing phase | from toe off to moment when tibia of the swinging limb is vertically oriented and plantar flexors and hip abductors rest |
| what is terminal swing phase | from vertical tibia of swinging limb to initial contact where hamstrings briefly work eccentrically to break forward leg movement |
| at the end of swing phase, what is activated | tibialis anterior is activated to antagonise movement of calcaneus upon impact |
| importance of tibialis anterior | is a key extensor (dorsiflexor) ehich is active over about 2/3 of the gait cycle where after a long march in an unaccustomed individual, it can swell and be painful in extreme cases leading to compartment syndrome |
Created by:
kablooey
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