Biomechanics/Kines Midterm Flashcards
kinematics
ROM
strength
speed
no regard to forces or torques
measured by goniometer and accelerator
kinetics
forces
torques
muscle/joint interaction
effect of forces and torques on body
measured by transducer
bones rotate around a plane that is…
… perpendicular to an axis of rotation
degrees of freedom
number of independent directions of movement allowed at a joint
up to 3
closed chain
proximal rotates against fixed distal
open chain
distal rotates against fixed proximal
convex-concave relationship improves
congruency
surface area for dissipating contact forces
helps glide motion between bones
three movements between joints
roll - changes contact surface
slide - same cs
spin - rotations, same cs
convex on concave
convex rolls and slides in opposite directions
concave on convex
concave rolls and slides in similar directions
where do articular surfaces fit best?
near end of ROM
called close packed position
provides stability to joint
loose packed position
ligaments slackened
increase in accessory movements
least congruent near midrange
when is the joint least congruent?
near the midrange
when is net force zero
when acceleration of mass is zero
not moving
what is the force that acts on body called?
a load
time of loading
how long
rate of loading
how fast
viscoelastic
tissues in which physical properties associated with stress/strain curve change as function of time
creep phenomenon
creep
progressive strain when exposed to constant load over time
reversible
rate-sensitivity of viscoelastic
increased stiffness affords greater protection to underlying bone at time when forces acting on joint are greatest
internal forces
within body
active or passive
external forces
outside body
gravity or external load
isometric
internal torque = external torque
2 ways to produce torque
1) force perpendicular to AoR
2) moment arm distance > zero
concentric
internal > external
eccentric
external > internal
mechanics
study of motion of objects and the forces that cause motion
rigid-body mechanics
assume rigidity
saves considerable mathematical and modeling work without a great loss of accuracy
moment arm
perpendicular distance between axis of rotation and line of force
torque/moment
force multiplied by moment arm
tends to rotate body
could by internal or external
internal force
within body
produced by active muscle
joint reaction force
in reaction to net effect of internal and external forces
if IT and ET are equal, JRF = 0
mechanical advantage
ratio of internal moment arm to external moment arm
output force to input force
MA = a/b = Fb/Fa
primary movement of human body
through rotations of its limbs and trunks
non linear movement
what are movement and posture based on?
instantaneous interaction between internal and external torques
lever
rigid bar that turns about an axis of rotation or fulcrum
rotates about axis as result of force
force acts against resistance
lever function
create MA
magnify force (MA > 1)
increase speed and ROM through which the end of the lever moves (MA < 1)
balance equal forces (MA = 1)
mnemonic for levers
FRE 123
class 1 lever
fulcrum in middle
MA <, >, or = to 1
designed for speed and ROM when fulcrum closer to force
designed for strength when fulcrum closer to resistance
class 2 lever
resistance in middle
MA is > 1
advantage for force - farce arm is longer
class 3 lever
effort in middle
MA is < 1
advantage in speed and ROM
statics
no acceleration
described as equilibrium
dynamics
acceleration is occurring
system is not in equilibrium
where to hold the bat?
bottom for more torque
chocked up for speed
what percent of all musculoskeletal complaints is the shoulder responsible for?
~16%
orientation of clavicle:
deviated about 20 degrees posterior to frontal plane
orientation of scapula:
deviated about 35 degrees anterior to frontal plane
retroversion of humeral head:
about 30 degrees posterior to medial-lateral axis at elbow
how many joints make up the shoulder complex?
4
AC, GH, SC, scapulothoracic (ST)
arthrokinematics: roll
multiple points along one rotating articular surface contact multiple points on another
arthrokinematics: slide
single point on one surface contacts multiple points on another
arthrokinematics: spin
a single point on one surface contacts a single point on another
roll, spin, slide - convex/concave relationship
convex - knuckle and arm, opposite movement
concave - cupped hand and arm, same movement
which part of clavicle is convex/concave?
longitudinal is convex
transverse is concave
SC arthrokinematics
depression: glide superior, roll inferior
elevation: glide inferior, roll superior
protraction: glide and slide anterior
retraction: glide and slide posterior
SC arthrokinematics - depression
depression: glide superior, roll inferior
SC arthrokinematics - elevation
elevation: glide inferior, roll superior
SC arthrokinematics - protraction
protraction: glide and slide anterior
SC arthrokinematics - retraction
retraction: glide and slide posterior
ST joint elevation
scapula slides sup on thorax
anterior tilting at AC
ST depression
from elevated position, scap slides inf on thorax
ST protraction
medial border of scap sides ant-lat on thorax away from midline
internal rotation at AC joint
ST retraction
medial border of scap slides post-med on thorax toward midline
ST upward rotation
inf angle of scap rotates sup-lat, faceing glenoid fossa upward
ST downward rotation
from upward rotated position, inf angle of scap rotates in inf-med direction
what happens at SC and AC during ST elevation
ST elevation
SC elevation
AC downward rotation
what happens at SC and AC during ST protraction
ST protraction
SC protraction
slight horizontal place adjustments at AC
what happens at SC and AC during ST upward rotation
ST upward rotation
SC elevation
AC upward rotation
relationship of elevation at SC and upward rotation at AC
most of SC movement occurs 20-90 degrees
AC movement picks up from 140-180 degrees
impingement can occur after 90 degrees
functional importance of upward rotation at ST
glenoid need to sit upward
slight upward rotation needed for length tension relationship
subacromial spaces maintained to avoid impingement
accounts for approximately 1/3 of near 180 degrees
of shoulder abd and flex
how much humeral head does glenoid fossa cover
only about 1/3
longitudinal head is 1.9 times larger
transverse head is 2.3 times larger
what is a slap tear
labral tears at the top of the glenoid
superior glenohumeral ligament
anatomic neck, above lesser tubercle
adduction, inferior and AP translations of humeral head
middle GH lig
along anterior aspect of anatomic neck; also bends with subscap tendon
anterior translation of humeral head, especially in about 45-60 degrees of abduction; external rotation
inferior GH lig: axillary pouch
as a broad sheet to the anterior-inferior and posterior -inferior margins of the anatomic neck
90 degrees of abduction, combined with AP and inferior translation
inferior GH lig: anterior band
as a broad sheet to the anterior-inferior and posterior -inferior margins of the anatomic neck
90 degrees of abduction and full external rotation; anterior translation of humeral head
inferior GH lig: posterior band
as a broad sheet to the anterior-inferior and posterior -inferior margins of the anatomic neck
90 degrees of abduction and full internal rotation
coracohumeral lig
anterior side of greater tubercle; also blends with superior capsule and supraspinatus tendon
adduction; inferior translation of the humeral head; external rotation
GIRD
glenohumeral internal rotation deficit
common in overhead athletes
GH and ST deficiency
20 degree or greater loss of internal rotation
high velocity abduction and external rotation during cocking phase
motion twists and elongates middle GH ligh and anterior band of inferior GH lig
active motion tends to translate humeral head anteriorly
throwing phases
wind-up
early cocking
late cocking
acceleration
deceleration
follow-through
injuries during late cocking
anterior GH instability
RTC
SLAP tear
quadrilateral space syndrome
medial elbow instability
capitellar OCD
injuries during acceleration
internal impingement
rotator cuff tear (RTC)
scapulothoracic bursitis
medial elbow instability
olecranon apophysitis / stress fx
injuries during decleration
RTC
SLAP tear
subacromial impingement
posteromedial elbow impingement
injuries during follow through
olecranon apophysitis
olecranon stress fracture
why is the glenoid labrum so vulnerable to injury?
only loosely attached to glenoid rim
~50% of fibers of tendon of long head of biceps direct extensions of superior glenoid labrum
glenoid fossa tilt
5 degree upward tilt relative to medial border of scapula
GH abduction
inferior glide
superior roll
GH adduction
superior glide
inferior roll
external rotation
(vertical axis)
anterior glide
posterior roll
internal rotation
(vertical axis)
posterior glide
anterior roll
flexion
anterior spin
extension
posterior spin
scapulohumeral rhythm
for every 3 degrees of shoulder abduction, 2 degrees by GH abduction and 1 degree by ST upward rotation
6 kinematic principles associated with full abduction of shoulder
- 2:1 SH rhythm shoulder abd 180 because 120 GH abd and 60 ST upward rotation
- 60 UR of scap because SC elevation and AC UR
- clavicle retracts at SC during shoulder abd
- scap posteriorly tilts and externally rotates during shoulder abd
- clavicle posteriorly rotates around own axis during shoulder abd
- GH externally rotates during shoulder abd
scapular statistics
medial border ~3” from spine
between T2-T7
flat against thorax and rotated 30-35 degrees anterior to frontal plane
SICK scapula
scapular malposition
inferior medial border prominence
coracoid pain and malposition
dysKinesis of scapula (lack of proper movement)
3 types of dyskinesis
- inferior medial scapular prominence
- medial scapular border prominence
- superomedial border prominence
1 and 2 associated with SLAP
3 associated with impingement and rotator cuff lesions
proximal stabilizers
originate on spine, ribs, and cranium
insert on scapula and clavicle
distal mobilizers
originate on scapula and clavicle
insert on humerus or forearm
ST elevators
upper trap
levator scapulae
rhomboids
support posture of shoulder girdle and upper extremity
ST depressors
lower traps
latissimus dorsi
pectoralis minor
subclavius
ST protractor
serratus anterior
forward pushing and reaching
final phase of pushup
ST retractors
middle trap - best
rhomboids
lower trap
middle trap has optimal line of force to retract scapula
active during pulling
scapular drifts into protraction of trap paralyzed
ST upper rotators
serratus anterior
upper and lower trap
ST downward rotators
rhomboids
pectoralis minor
muscle produces torque at a joint if
- produces force in plane perpendicular to AoR (axis of rotation) of interest
AND
- acts with associated moment arm distance > zero
three groups of elevators
- elevate humerus at GH
- scapular muscles that control upward rotation of ST
- rotator cuff that control dynamic stability at GH
muscles responsible for elevation of arm by group
GH muscles
~ anterior and middle deltiod
~ supraspinatus
~ coracobrachialis
~ biceps long head
ST
~ serratus anterior
~ trap (upper and lower)
RC
~ supra
~ infra
~ teres minor
~ subscap
which RC have limited moment arm to abduct GH joint?
upper fibers of infraspinatus and subscapularis
supraspinatus role in shoulder abduction
rolls humeral head superiorly while also compressing joint
how cuff muscles control abduction at GH
supra: main compressor, drives superior roll
infra, TM, sub: exert depression on humeral head
infra and TM: externally rotate humerus
serratus anterior paralysis
downward rotated scapula - flaring
winging scapula
shortening of pec minor
subacromial impingement syndrome
most common painful disorder of shoulder
supra tendon, biceps long head tendon
“when I raise my arm, it hurts”
abd of 60 - 120 called the painful arc
possible causes of impingement syndrome
- abnormal kinematics at GH and ST
- slouched posture affecting ST alignment
- fatigue, weakness, poor contorl, tightness of GH & ST muscles
- inflammation and swelling in and around subacromial space
- excessive wear and subsequent degeneration of tendons of rotator cuff
- instability of GH
- adhesions in inferior GH
- excessive tightness in posterior GH
- osteophytes forming aroung AC
- abnormal shape of acromion or coracoaromial arch
where does slap tear affect.
posterior band of inferior GH lig
what does GIRD affect
posterior band of the inferior GH lig
Is motion of shoulder required for supination and pronation of the palm?
no
what joints make up the elbow and forearm complex?
humero-ulnar
humero-radial
proximal radio-ulnar
distal radio-ulnar
what provides stability at humero-ulnar joint?
tight fit between trochlea and trochlear notch
what type of joint is the elbow?
ginglymus or hinged
modifies hinge because there is slight axial rotation as it flexes/extends
what is the normal angle of the elbow
15 degrees valgus
ulna deviates laterally relative to humerus
carrying angle
valgus deformity - 30 lateral
varus deformity - 5 medial
who would have greater carrying angle between men and women?
women by 2 degrees
greater on dominant arm regardless of gender
valgus when elbow is extended
exceeds ~20-25 degrees
gunstock deformity
varus deformity where forearm deviated toward midline
can be born with it
what form of trauma can varus/valgus deformity result from?
severe fracture through growth plate of distal humerus in children
excessive valgus may damage ulnar nerve as it cross medial to elbow. it will slip in and out of the groove
articular capsule of elbow
encloses HU, HR, and PRU
thin and reinforced anteriorly by oblique bands of
fibrous tissue
synovial membrane lines internal surface of capsule
collateral ligaments stregnthen …
articular capsule
they provide an important source of stability to elbow joint
medial collateral ligament
anterior fibers: strongest and stiffest, commonly torn by throwers, most significant resistance against valgus
posterior fibers
transverse fibers:
anterior fibers of MCL
origin: medial epicondyle
insertion: medial coronoid process
taught through sag plane movement (flex/ext)
provide articular stability throughout entire ROM
posterior fibers of MCL
origin: posterior medial epicondyle
insertion: medial olecranon process
resist valgus and extreme elbow flexion
transverse fibers of MCL
cross from olecranon to coronoid
do not resist anything
dynamic medial stabilizers
proximal fibers of wrist flexor and pronator groups
resist excessive valgus at elbow
most important: flexor carpi ulnaris
fall onto an outstretched arm and hand (FOOSH)
fully extended elbow forced into excessive valgus
may result in fracture of radius, ulnar nerve, anterior capsule or MCL injury
how much compression force does radius absorb?
80%
lateral collateral lig
origins on lateral epicondyle and immediately splits into two fiber bundles
taut during full flexion
stabilize during varus
radial collateral lig
fans from lateral epicondyle to blend with annular lig
lateral (ulnar) collateral lig
spans from lateral epicondyle and inserts to superior crest of ulna
guy wires of elbow
LUCL and AMCL
provide medial-lateral stability to ulnar during sag plane movement
what does rupture of LCL cause?
varus of elbow and posterior lateral rotary instability
expressed as excessive external rotation of forearm
motions that increase tension in CL of elbow
AMCL - valgus, ext/flex
PMCL - valgus, flex
LRCL- varus, external rotation
LUCL - varus, external rotation, flex
annular- distraction of radius, external rotation
elbow flexion contracture
muscles abnormally stiff after long periods of
immobilization in flexed and shortened position
increased stiffness may occur in anterior capsule and
some anterior fibers of MCL
tightness in flexors if cannot fully extend
in what activities does elbow extension occur?
throwing
pushing
reaching
maximal range of passive ROM generally available to elbow
5 degrees beyond neutral extension through 145 degrees of flexion
functional arc of elbow
30 - 130 degrees of flexion
loss of extremes usually results in only minimal functional impairment
humero-ulnar joint articulation
concave trochlear notch of ulna
convex trochlea of humerus
motion limited to sagittal plane
how much of articular surface does hyaline cover of trochlea and trohlear notch?
trochlea - 300 degrees
notch - 180 degrees
what stabilizes healthy HU joint in extension?
articular congruency and increased tension in stretched connective tissues
humero ulnar joint flexion
roll and slide superior
HUJ dislocation
trochlear notch of ulna may dislocate posterior to trochlea of humerus in severe elbow injuries
caused by FOOSH
HRJ articulation
between cuplike fovea of radial head and reciprocally shaped rounded capitulum
HRJ flexion
roll and slide superiorly
explain the motion of supination and pronation
occurs around an axis of rotation that extends from radial head through ulnar head - an axis that intersects and connects both radio-ulnar joints
when are radius and ulnar parallel?
in full supination
when does radius cross over ulna?
in full pronation
thumb will stay with radius in pronation
what is the midway between complete pronation and supination?
thumbs up position
what are the average ROM’s through pro/sup
pronation: 75 degrees
supination: 85 degrees
several ADLs require only 100 degrees rotation, 50 pro through 50 sup
how many degrees of rotation can a person lack and still complete ADLs?
30 degrees
how to compensate for pro/sup?
pronation: internally rotating shoulder
supination: externally rotating shoulder
supination at PRUJ
rotation of radial head with fibro-osseous ring formed by annular ligament and radial notch of ulnar
which arm bone is fixed in open chain sup/pro?
ulna
DRUJ supination (open chain)
roll and slide inferior
PRUJ supination (open chain)
external rotation
DRUJ pronation (open chain)
roll and slide superior
PRUJ pronation (open chain)
internal rotation
screw home of elbow
proximal migration of radius and increased joint compression of HRJ
PRUJ pronation (closed chain)
external rotation
DRUJ pronation (closed chain)
slide posterior, roll anterior
PRUJ supination (closed chain)
internal rotation
DRUJ supination (closed chain)
slide anterior, roll posterior
force-couple
used to pronate forearm from weight bearing position
infraspinatus rotates humerus relative to fixed scapula, whereas pronator quadratus rotates ulna relative to fixed radius
arthrokinematics of pro/sup at PRUJ while weight bearing
annular lig and radial notch of ulna rotate around fixed radial head
arthrokinematics of pro/sup at PRUJ while non-weight bearing
radial head rotates within ring formed by annular lig and radial notch of ulna
arthrokinematics of pro/sup at DRUJ while weight bearing
convex ulnar head rolls and slides in opposite direction on concave ulnar notch of radius
arthrokinematics of pro/sup at DRUJ while non-weight bearing
concavity of ulnar notch of radius rolls and slides in similar directions on convex ulna head
function of elbow muscles
muscles that attach distally on ulna flex/extend but do not pro/sup
muscles that attach distally on radius my flex/extend but also can pro/sup
primary elbow flexors
biceps brachii
brachialis
brachioradialis
pronator teres
brachialis has larger …
(biomech variables)
volume: 59.3 cm3
physiologic cross-sectional area: 7.0 cm2
brachioradialis has larger …
(biomech variables)
internal moment arm: 5.19 cm
biceps brachii O/I
origin on scapula
insertion on radial tuberosity on radius
biceps brachii EMG signal
maximal when both flexion and supination simultaneous
low signal when flexion with pronation
brachialis O/I
origin: anterior humerus
insertion: proximal ulna
brachialis sole purpose
to flex elbow
expected to generate greatest force of any muscle crossing elbow
brachioradialis O/I
origin: lateral supracondylar ridge of humerus
insertion: styloid process of radius
what is the longest of all elbow muscles?
brachioradialis
what does maximal shortening of brachioradialis cause?
full elbow flexion and rotation of forearm to near neutral position