BM unit 3

Question 1

segments of the lower limb

Answer 1

thigh, leg, foot

Question 2

three major joints in lower limb

Answer 2

hip, knee, ankle

all synovial

Question 3

describe the hip joint and movements

Answer 3

ball and socket
ball = head of femur
socket shaped acetabulum of the pelvic girdle
allows flexion, extension, abduction, adduction, internal and external rotation
ball and socket also allows circumduction where the femur moves in a circle relative to the pelvis

synovial joint - surfaces of bone covered in artic cartilage, enclosed in a sleeve of tough fibrous tissue, the joint capsule, which forms the synovial cavity which is filled with synovial fluid which lubricates and provides nutrients to artic cartilage. synovial fluid is produced by the synovial membrane which lines the inner surface of the capsule.

joint is surrounded by strong articular joint capsule and ligaments which are surrounded by strong muscles - these along with ball and socket shape make the hip intrinsically stable. this means dislocations of the hip in adults is rare.

Question 4

range of motion of hip joint

Answer 4

ROM greatest in sagittal plane, where flexion extension occur
flexion - 0-140
extension - 0-20

forntal plane
abduction - 0-30
adduction - 0-25

transverse plane
external rotation - 0-90
internal rotation - 0-70 when the hip is flexed

Question 5

ROM needed in hip for daily life

Answer 5

120 flexion extension

20 abduction-adduction and rotation

Question 6

examine bilateral stance and forces at the hip joint

Answer 6

bilateral stance - no muscles active at the hip joint so we only need ti consider external forces - weight of upper body, two reaction forces one at each hip joint.

upper body =70% weight
each lower limb = 15%

work out by solving moments about each hip joint. from this analysis we can conclude that during normal bilateral standing the forces acting at the hip joints are hip joint are vertical and equal to half the upper body weight.

Question 7

examine unilateral stance and forces at the hip joint

Answer 7

during unilateral stance abductor muscle activity is required to stabilise the position of the body.
4 forces - weight of the lower limb, abductor muscle force, joint force at the hip, ground reaction force

divide abductor muscle force into two components (acts at 70 degrees to the horizontal. joint force also has two components
reaction force = total body weight
one lower limb = 15% body weight

solve by moments and trig

force is larger than during bilateral stance as only one hip supports whole body weight, most of the increase is due to the contraction of hip abductor muscles which pulls the two sides of the hip joint together and by doing so increases the force at the hip.

p7 do the example yourself

Question 8

what is the largest joint in the body

Answer 8

knee

Question 9

two articulations in the knee joint

Answer 9

patellofemoral and tibiofemoral (most of the movement due to this joint - patellofemoral assists)

Question 10

describe the knee joint

Answer 10

proximal surface of the tibia is flat and covered with the menisci (2 crescent shaped pieces of fibrocartilage thata re attatched to tibia by short tough ligaments. menisci make teh flat top of the tibia slightly concave which aids stability. they also act as load distributors and shock absorbers.

distal end of the femur s formed by two circular shaped condyles - fem condyles. they are covered in artic cartilage. the smooth anterior depression between them is called the intercondular notch. the cruciate ligaments which help bind the femur and tibia are lodged in this notch.

the patella is the largest sesamoid bone (a bone found in a tendon). its in the tendon of the quadriceps femoris muscle. the posterior surface of the patella has two smooth articular surfaces either side of a slight central ridge. the two articular surfaces articulate with the respective femoral condyle. the ridge guides the patella along the groove between the femoral condyles as the knee joint flexes and extends.

the fibular doesn’t form part of the knee joint, but it does act as an anchor for the biceps femoris muscle and lateral collateral ligaments.

the shape of the bones that form the knee joint dont contribute much to its stability - most of the stability is derived mainly from its ligaments
within the joint the the ACL and PCL cross each other in the centre of the joint - they limit forward and backward sliding of the femur on the tibia and limit hyperextension. the joint is surrounded by a fibrous joint capsule which is thickened around the posterior on the medial and lateral sides. outside the capsule on either side lie the medial and lateral collateral ligaments which prevent adbuction and adduction. the quadriceps muscle also aids stability as do the menisci, especially during rotation

Question 11

what type of joint is the knee

Answer 11

generally a hinge - (rotates about the same axis) - but this isnt true for the knee as its axis of rotation changes as it flexes and extends.
if the sagittal plane is considered then the centre of the joint moves in a semicircle as the condyles are not perfectly circular and because of restrictions from ligaments. deformities of the knee joint surfaces cause the centre of rotation to follow more complex patterns

when rotation is studied in all three dimensions it becomes apparent the knee is a hinge joint with a moving axis of rotation. it has a screw home mechanism where it follows a spiral motion. as the knee flexes the tibia rotates internally and as the knee extends the tibia rotates externally. the spiral motion is a consequence of the diff sizes of lateral and medial condyles (medial is longer than the lateral)

in addition to rotation, knee also has limited abduction and adduction and internal and external rotation

Question 12

ROM in kenn joint

Answer 12

attributed to the tibiofemoral joint

sagittal plane:
few degrees of extension
flexion - 140

frontal plane:
depends on how much the knee is flexed - adbuction and adduction occur only at a max of a few degrees when knee is flexed to 30

transverse plane:
internal 0-30
external 0-45
also depends on the knee being flexed - 90 flexion makes the biggest rotation possible
at full extension rotation is almost completely inhibited by the interlocking femoral and tibial condyles

Question 13

ROM for knee for daily life

Answer 13

full extension to 115 of flexion

10 of rotation

Question 14

function of the patella and what happens if you remove it

Answer 14

increase the lever arm of the quad femoris muscle. it assists knee extension by increasing the lever arm of the quads muscle by displacing the quad tendon.
quad femoris provides the effort force needed to maintain the knee joints position, overcoming the resistive force. ground reaction force is produced by the weight of the body acting behind the knees. the lever arm of the quads muscle is dependent on the position of the patella which in turn is dependent on the amount of flexion-extension. at full extension the quads tendon is displaced anteriorly lengthening the lever arm considerably. as the knee flexes the contribution of the patella to the length of the lever arm decreases as the patella sinks into the intercondylar notch. at full flexion the patella is located in the intercondylar notch where it contributes little to the effort arm.
(flex the knee beyond 90 and you feel the depression between the condyles (trochlear) above the patella. then extend the knee and you feel the patella rising up the trochlear)

if the patella is removed (paellectomy) the lever arm is reduced. to compensate for this the force produced by the quads muscle must increase considerably to provide the required turning moment.

Question 15

function of the menisci and what happens if they are removed

Answer 15

act as force distributors and shock absorbers between the femur and the tibia. they distribute force over the entire surface of the tibial plateau - since its distributed over a large area the stress in the artic cartilage and underlying bone tissue is small. if menisci are removed then force isnt distributed and instead focused on the point between the tibia and femur - this increases the stress in the joint tissues and will increase the likelihood of wear and joint damage. three fold increase un stress when menisci are removed

Question 16

describe teh ankle joint

Answer 16

essentially a hinge synovial joint formed by the distal ends of the tibia and femur and talus. three articulations - tibiotalar, fibulotalar and distal tibiofibular.

two bony prominences - medial and lateral malleolus. lateral is made up of the distal end of the fibular, medial is made of the distal end of the tibia

bones that form the ankle joint are intrinsically stable like the hip. but more stability is needed due to the high loads it withstands. ligaments surround the joint - three most important are anterior inferior talofibular ligament, medial ligament and lateral ligament

Question 17

ankle joint motion

Answer 17

axis of rotation corresponds to the line joining the lateral and medial malleolus

flexion = dorsiflexion
extension = plantarflexion
ROM varies but is usually around 45 (10-20 dorsi and 25-35 plantar)

during walking motion varies from about 10 of dorsi and 15 of plantar

Question 18

describe the common sprained ankle

Answer 18

partial tear of the anterior inferior talofibular ligament resulting from a sudden adduction of the foot whilst the ankle is plantarflexed

Question 19

three parts of teh foot

Answer 19

hindfoot, midfood, forefoot

Question 20

describe teh hind foot

Answer 20

talus, calcaneus

Question 21

midfoot

Answer 21

cuboid, medial, intermediate and lateral cuniforms and the navicular

Question 22

forefoot

Answer 22

metatarsals and phalanges

Question 23

describe the subtalar joint

Answer 23

between the talus and calcaneus
joint has an oblique axis positioned at 42 degrees to the plantar surface and 16 degrees medial to the midline of the foot

it allows inversion (inward rotation so plantar surface faces medially) and eversion (external rotation so plantar surfaces faces laterally) to occur.
inverted by 20
everted by 5
during walking the range of motion is about 6

Question 24

describe the arched structure of the foot and what happens when you dorsiflex the toes

Answer 24

two way arched structure formed from the bones of the foot and kept in place by ligs.

5 longitudinal arches that extend from the clacaneus along the 5 sets of tarsals and mets. the longitudinal arch is supported by the plantar fascia which extends from clacaneus to attach to the plantar aspect of the prox phalanges. it is a heavy ligamentous structure that may only be elongated slightly when loaded. t functions as a cable between the heel and toes and as a shock absorber.

transverse arch runs across the foot.

during standing the bones of the longitudinal arch and the plantar fascia act like a truss. the plantar fascia prevents the vertical force acting downwards at the ankle joint from collapsing the longitudinal arches.

when toes are dorsiflexed the plantar fascia is put under tension and the two ends of the foot are drawn together raising the longitudinal arches. the bones of the foot are then held together tightly and function as a single unit rather than separate bones.

Question 25

describe reciprocal gait

Answer 25

lower limbs are used alternatively to provide support and propulsion

Question 26

what is a swing through gait

Answer 26

eg if someone has a broken femur they use crutches to support and both legs swing through and land ahead of the crutches

Question 27

what is gait analysis

Answer 27

clinical examination of the gait
may be used to determine surgical intervention to improve the gait of a CP child . used to quantify the severity of a disease or determine the outcome of an operation. can also be used to ensure the best alignment of an artificial leg.

Question 28

what are gait labs and what do they have

Answer 28

equipped with motion analysis systems, force plates, electromyography equipment. means gait can be studied but also other common movement of daily life eg sitting, standing, sports.

Question 29

what is motion analysis and how is it used

Answer 29

cameras see special markers, each marker must be seen by two or more cameras for the system to be able to calculate the position of each marker in 3D.movement of the patient can be constructed using computer. so you can view patient from any angle and obtain quantitive data eg joint angles which you can compare to a database of data of able bodied people.
often integrated with force plates to measure ground reaction forces and EMG to measure muscle activity

Question 30

what is the gait cycle

Answer 30

to understand reciprocal gait
walking pattern divided into gait cycle
gait cycle = one stride which is equal to two steps
it starts with initial contact with ground, heel contact, and ends with the next heel contact pf the same foot

Question 31

describe the parts of the gait cycle and the characteristic events
describe foot drop and who might suffer from this

Answer 31

each foot is in contact with the ground for part of the cycle - stance phase , and for the rest it loses contact with the ground so is called swing phase

there is a period of time where both feet are down = double support. as speed of locomotion increases, double support time decreases until there is no double support ie running

reciprocal gait is characterised by a number of events:

• heel contact
• foot flat
• mid stance
• heel off
• toe off
• mid swing

the stance phase lasts from heel contact to toe off, and wing from toe off to next heel contact

one or two events may be missing in the gait of a person with a disorder eg mild stroke or weak dorsiflexor muscles may experience foot drop - foot hangs down during swing phase so the toes make contact with the ground before the heel does.

Question 32

range of joint motion in lower limb during reciprocal gait

Answer 32

hip
- 15 extension to 30 flexion

greatest ROM is at knee
- few degree of extension to 70 flexion

lowest ROM is at ankle

• 15 plantarflexion to 10 dorsiflexion
• two main peaks of plantarflexion - foot flat and just after toe off
• peak dorsiflexion at heel off as the foot is left trailing behind the rest of the body

Question 33

ground reaction forces during the gait cycle

Answer 33

magnitude and direction varies during the stance phase
in the sagittal plane it creates a butterfly diagram - characterised by a double hump.
first hump = due to the deceleration of body mass as the weight is transferred on to the foot
second hump = due to the foot pushing off the ground

Question 34

forces and moments that can be measured during walking

describe the moments about the hip, knee and ankle during walking

Answer 34

external forces and moments acting on the foot measured using force plates
weight and anthropometric data can be collected
forces by muscles and tension in the ligs by EMG and mathematical models

at the hip, after heel contact, there is a positive extension moment produced by the hip extensors to prevent upper body falling forward. At the knee, just after heel contact, there is a small flexion moment as the hamstrings contract to prevent hyperextension of the knee. This changes to an extension moment as the quadriceps contract to prevent the knee from buckling. At the ankle the plantarflexion moment increases to a peak just before toe off as the triceps surae contracts to push the foot up and off the ground - look at graphs on p 29