Biomechanics Flashcards
1
Q
What is Nutation
A
anterior tilt of the base of the sacrum relative to the ilium
2
Q
What is counternutation
A
Posterior tilt of the base of the sacrum relative to the ilium
3
Q
the effect of angle of femur - good or bad?
A
can have positive or negative biomechanical effects
4
Q
Coxa vara
A
- smaller angle
- distal is more medial
- <125 degrees
5
Q
coxa valga
A
- larger angle
- distal is more lateral
- > 125 degrees
6
Q
cause of change in femur neck angle inclination
A
may change as a result of a hip fracture or specific design of prosthetic hip
7
Q
Describe femoral on pelvic motion
A
The movement of the femur upon a relatively fixed pelvis
8
Q
Describe pelvic on femoral motion
A
The movement of the pelvis upon the relatively fixed femur
9
Q
Anterior pelvic tilt will result in hip joint _
A
flexion
10
Q
posterior pelvic tilt will result in hip joint _
A
extension
11
Q
Hiking the contralateral iliac crest creates _
A
abduction
12
Q
lowering the contralateral iliac crest creates_
A
adduction
13
Q
osteokinematic movements of the hip
A
flexion/extension
Abduction/adduction
rotation
14
Q
Degrees of hip flexion
A
120 degrees
15
Q
Degrees of hip extension
A
20 degrees
16
Q
Flexion of knee impact on hip flexion
A
with flexed knee - 120 degrees
with extended knee 70 degrees - due to the tension in the posterior thigh muscles
17
Q
degrees of hip abduction
A
40 degrees
18
Q
degrees of hip adduction
A
25 degrees
19
Q
degrees of neutral hip internal rotation
A
35 degrees
20
Q
degrees of neutral external hip rotation
A
45 degrees
21
Q
osteokinematics of hip flexion/extension
A
sagittal plane, medial-lateral axis
22
Q
osteokinematics of hip abduction/adduction
A
frontal plane, anterior-posterior axis
23
Q
osteokinematics of rotation in neutral position
A
horizontal plane, vertical axis
24
Q
osteokinematics of hip rotation at 90 degrees flexion
A
frontal plane, anterior-posterior axis
25
which muscles help single leg stance
gluteus medius, minimus and tensor fascia lata (the hip abductors)
Create pelvic on femoral abduction which offsets the adduction force of the body weight
26
Hip abductor moment arms -when the hip abductor torque can't offset the body weight torque ...
the pelvis will drop to the contralateral side
27
Trendelenburg's sign
When the pelvis drops to the opposite side during a single-leg stance
28
The angle between lateral aspect of the femur and tibia
170-175 degrees
29
Genu valgum
Decreased angle at the lateral aspect of the knee
Approx less than 170 degrees
"knock knees"
30
Genu Varum
Increased angle at lateral aspect of the knee
greater than 180 degrees
"bow legged"
31
excessive genu valgum places increased load on the ___ aspect of the knee
lateral
32
excessive genu varus places increased load on the ___ aspect of the knee
medial
33
How could genu valgum and genu varus affect the patellofemoral alignment
as the patella sits in the middle of the longitudinal axis od rotation of the lower limb, any deviation can also affect patellofemoral mechanics
34
What is the Q angle
A measurement of the angle of the quadriceps pull
It is determined by the intersection of
1. a line running from the central patella to the anterior superior iliac spine (the force of the quadriceps)
2. a line intersecting the tibial tuberosity and middle patella
13-15 degrees - varies
(due to the oblique angle of the femur, when the quadriceps femoris muscle contracts, it pulls the patella superiorly and in a small degree laterally
35
Factors influencing the Q angle and patella position
Global factors - related to the alignment of bones and joints
- sex, excessive genu valgum, tibial torsion(rotation), foot mechanics (pronation, supination)
36
Patellofemoral joint factors
- forces should be balanced to allow it to move optimally during flexion and extension
- if not balanced, it will not track efficiently - leading to increased stress of articular surfaces and risk of dislocation
37
Osteokinematics of knee flexion/extension
sagittal plane, medial-lateral axis
38
osteokinematics of knee internal and external rotation
horizontal plane, vertical axis
39
what muscles cause internal and external rotation of the knee
Posterior muscles of the thigh
- plus sartorius medially
40
Tibial on femoral knee rotation - rotation is ___ as tibia motion
the same
(tibia moves in = internal rotation)
41
Femoral-on-tibial knee rotation - rotation is ___ as femur motion
opposite
(femur moves in = external rotation)
42
femoral on tibial flexion arthokinematics
The convex femur roll posteriorly and slide anteriorly on concave tibia
43
femoral on tibial extension arthrokinematics
convex femur rolls anteriorly and slides posteriorly on concave tibia
44
tibial on femur flexion arthrokinematics
concave tibia rolls and slides posteriorly on convex femur
45
tibial on femural extension arthrokinematics
concave tibia rolls and aglides anteriorly on the femoral condyle
46
Screw-home mechanicsm of locking knee joint
small smount of rotation occurs as the knee approaches full extension
results in maximum congruence of the joint surfaces(ligaments are taught, menisci tightly interposed between condyles,
47
Locking of the knee is driven by
1. shape of the femoral condyles
2. passive tension in the ACL
3. the slight lateral pull of the quadriceps femoris
48
Tibial on femoral locking/unlocking
open chain knee extension where the tibia is free to move on the femur.
From 30 degrees of flexion into full extension, the tension is the ACL and lateral pull of the quadriceps creates EXTERNAL rotation
49
Femoral of tibial locking unlocking, closed chain reaction where the femur moves upon the fixed tibia,
the shape of the femoral condyles and tension n the ACL ligament produce slight INTERNAL rotation of the femur
50
Role of the patella
works as an anatomical pulley and mechanism to reduce friction between the quadriceps and femoral condyles
It increases the moment arm of the knee extensor mechanism by displacing the tendon of the quadriceps anteriorly
Therefore it enanhances the extension torque produces by quadriceps femoris
51
Joint reaction force
The force which occurs within a joint due to the forces acting upon that joint (muscle contraction and gravity)
52
patella joint force is influenced by_
1. pull of the quadriceps femoris muscle and patella tendon
2. degree of knee flexion
53
Forces of the patellofemoral joint
lateral directed forcesforces:
iliotibial band
bowstringing force on the patella
pateral patellar retinaculr fibers
medial directed forces:
vastus medialis (oblique fibers)
raised lateral facet of the intercondylar groove
medial patellar retinacula fibers
54
the ACL resists...
knee extension
anterior translation of the tibia on femur
posterior translation of femur on tibia
55
Injury vectors of the ACL
hyperextension
rotation
valgus force
56
the PCL resists...
knee flexion
posterior translation of the tibia on the femur
anterior translation of the femur on the tbia
57
injurh vectors of the PCL
hyperflexion
posterior translation
58
the MCL resists...
valgus
extension
59
injury vectors of the MCL
valgus
hyperextension
60
the LCL resists
Varus
extension
61
injury vectors of the LCL
varus
hyperextension
62
osteokinematics of talocrural dorsi/plantarflexion
sagittal plane, medial-lateral axis
63
arthrokinematics of talocrural dorsiflexion
the convec talus rolls anteriorly and slides posteriorly on the concave mortice of the tibia and fibula
64
arthrokinematics of talocrural plantarflexion
the convex talus rolls posteriorly and slides anteriorly on the concave mortice of the tibia and fibula
65
combined movements of pronation
Dorsiflexion
abduction
eversion
66
function of ankle pronation
the spring is storing energy
provides shock and energy absorption through the gait cycle
67
when does foot pronatioon interchange to supination
once the 1st metatarsophalangeal joint engases with the ground
68
combined movements of supination
plantarflexion
adduction
inversion
69
function of foot supination
the spring is releasing energy
energy release stage of the gait cycle
energy is used to propel the limb through the next step nd set up for the next landing
70
factors influencing the stability of the ankle joint
1. the shape of the tibia, fibula and talus
2. ligaments (anterior and posterior talofibular, calcaneofibular, deltoid ligaments, inferior tibiofibular joint ligaments)
3. leg muscles (inverters and evertors)
4. effective proprioception
71
most stable ankle joint position
dorsiflexion
72
least stable ankle joint position
plantarflexion
73
active insufficiency
occurs when a multi-joint muscle reaches a shortened length where it can no longer apply an effective force
actin and myosin filaments are overlapping - cant createconcentric force
74
passive insufficiency
the inability of a multi-joint muscle to lengthen to a degree that allows full range of motion of motion of all the joints it crosses simultaneously
sarcomeres are stretched to their limit
75
key supporting ligaments of the plantar surface
1. plantar calcaneonavicular ligament -spring lig
2. plantar calcaneocuboid ligament - short plantar lig
3. long plantar lig - b/w calcaneus and cuboid - superficial to short lig
76
plantar aponeurosis function
structural support
supports longitudinal foot arch
protection of sole from injury
77
Weight of the lower limb is transferred to the ground posteriorly by...
medial process of the calcaneal tuberosity
78
Weight of the lower limb is transferred to the ground anteriorly by...
heads of the metatarsals
79
the function of foot arches?
Shock absorption as the foot strikes the ground
Flexibility to adapt to body weight distribution and variable ground surfaces
Propel the body during walking, running and jumping
80
medial longitudinal arch
higher and more important
Formed by - calcaneus, talus, navicular, three cuneiforms, 1-3 metatarsals
81
lateral longitudinal arch
flatter and typically on the ground when standing
Formed by - calcaneus, cuboid, 4-5 metatarsalsF
82
transverse arch
runs from side to side
Helf up off the ground by the longitudinal arch
Formed by - cuboid, 3 cuneiforms, bases of the metatarsals
83
The arches of the foot are passively supported by...
1. shape of the bones
2. plantar ligaments (spring lig, short plantar lig, long plantar lig)
3. Fascia (plantar aponeurosis)
84
The arches of the foot are dynamically supported by
1. The bracing action of intrinsic foot muscles
2. Tonic contraction of extrinsic foot muscles via their long tendons in the foot
85
the longitudinal arch is supported by which muscles?
Flexor hallucis longus and flexor digitorum longus
86
the transverse arch is supported by which muscles?
tibialis posterior and fibularis longus
87
Windlass mechanism
When the winding up of the plantar fascia, due to extension of the MTP, causes increased tension and raising of the medial longitudinal arch to create supination and sets up the swing of the foot
88
Pec cavus
Higher arches
may result is more rigid joints of the foot and forefoot, less flexibility and therefore affecting the ability to dissipate forces during pronation of the foot
89
Pes Planus
flattened arches
The medial longitudinal arch is typically poorly supported and reduced extension of the MTP joints limits the ability of the windlass mechanism to occur
90
conditions affecting motion of the big toe
Osteoarthitis, gout, affecting joints and mobility of the foot
91
conditions affecting mechanics of the lower limb
genu valgus, varus
92
The gait cycle
The activity that occurs between the time the foot of one lower limb touches the floor and when the same foot touches the floor again
93
stance phase
the period of activit that occurs when the foot is in contact with the ground
94
phases in the stance phase
* Heel contact - heel contacts floor (pronated)
* Flat foot - entire plantar surface contacts floor
* Mid stance - body's weight passes directly over
* Heel off - heel comes off ground
* Tow off - toe comes off (supinated)
95
swing phase
when the foot is in the air, being advanced forward for the next contact with the ground
from toe off to heel contact of the same foot
96
percentage of gait cycle in the stance phase
60%
97
percentage of gait cycle in the swing phase
40%
98
phases of the swing phase
* Early swing - toe of to mid (plantarflexion to neutral position)
* Mid swing
* Late swing - mid to heel contact (relatively full dorsiflexion)
99
typical type of muscle contraction when pronating?
eccentric contraction
100
typical type of foot muscle contraction when supinating
101
The lateral compartment of the leg is most active in what phase?
Stance phase - throughout mid stance and push off
(support transverse and medial longitudinal arches+ stabilise joint)
102
The posterior compartment of the leg is most active in what phase?
Stance phase - floot flat and toe off
Foot flat to heel off - eccentrically (decelerate)
Heel off to toe off - concentrically
