Week 1

Question 1

DEGREES OF FREEDOM

Answer 1

Number of independent directions of movement

Can have up to three degrees of freedom (corresponding to 3 cardinal
planes)

Stability vs mobility

Question 2

AXIS OF ROTATION

Answer 2

Pivot point about which motion is occurring
In what plane does the axis lie?

Importance of knowing the location of axis of rotation

The plane of the axis of rotation is perpendicular to the plane of the osteokinematic
motion

Able to determine muscle actions – Application!!!

Question 3

Translation

Answer 3

surface to surface motion

linear motion

arthokinematics: slide

Question 4

Rotation

Answer 4

circular motion

osteokinematics:
flex/ext = sagittal
ab/adduction = frontal
int/ext rotation = transverse

arthrokinematics:
roll spin

Question 5

Internal force

Answer 5

muscles - active and passive

Can be active (stimulated muscle under volitional control) or passive (generated by tension in stretched periarticular
connective tissues, such as intramuscular fascia, ligaments, joint
capsule)

ligaments and tendons

joint capsules

compression force
tension
shear force

Question 6

External force

Answer 6

COM

Friction

Gravitational force – pulling on mass of body, a body segment,
or an external load

Contact force – push, pull

Question 7

MechA =

Answer 7

IMA/EMA

Question 8

Kinematics

Answer 8

Branch of mechanics that describes:
* Motion of the body (joints) without regard to forces or torques that may
produce motion

2 types of motion
* Translation – Linear motion
* Rotation – Angular motion

Question 9

Translational/Linear motion

Answer 9

Joint surface to surface motion- all parts of a body/segment move parallel to and in the same direction as the other parts of a body/segment (can be in a
straight line or curved path)
* Sliding in knee extension

Question 10

Rotational/Angular motion

Answer 10

Circular motion

Body moves about a pivot point, so all points of the body simultaneously rotate
in the same angular direction

Motion of two adjacent long bones relative to each other

Question 11

Axis of rotation

Answer 11

Pivot point for the angular motion

Center of rotation
* Changing throughout joint movement
* Bones rotate about a joint in a plane that is perpendicular to the axis of rotation

Question 12

Osteokinematics

Answer 12

Motion of bones relative to the 3 cardinal planes of the body (person in
anatomic position)

Movement can occur in 2 different ways
* Proximal segment can rotate against the relatively fixed distal segment (closed chain)
* Distal segment can rotate against the relatively fixed proximal segment (open chain)

• “Knee flexion” describes “relative motion”;
• Does not tell you which segment is moving
  -i.e. tibial on femoral or femoral on tibial

Question 13

open chain

Answer 13

proximal segment fixed

distal segment free

Question 14

closed chain

Answer 14

proximal segment free

distal segment fixed

Question 15

Kinematic chain

Answer 15

refers to series of articulated segmented links

i.e. scapula, humerus, ulna/radius, carpals

Question 16

Closed chain

Answer 16

the distal end of the extremity is fixed to the earth or other immobile object

e.g. squat, pull up

Question 17

Open chain

Answer 17

distal end of the extremity is not fixed and is free to move

e.g. knee extension machine, bicep curl

Question 18

Arthrokinematics

Answer 18

Describes motion that occurs between the articular surfaces of the joints

Joint surfaces range from flat to curved

One surface usually relatively convex, one concave

Helps to improve joint congruency, dissipate forces by increasing the
surface area, and guide the motion between bones

Question 19

3 fundamental arthrokinematic movements:

Answer 19

spin
roll
slide/glide

Question 20

Spin

Answer 20

Bone can also rotate by spinning its articular surface against the articular surface
of another bone (radio humeral joint)

Question 21

Roll and glide

Answer 21

Rolling convex surface typically involves slide in the opposite direction

Many joints combine rolling and slide with spinning (e.g., femoral on tibial knee
extension the femur spins internally as the femoral condyle rolls and slides on the
relatively fixed tibia)

Question 22

Convex-Concave Rule

Answer 22

Direction of arthrokinematics rolling and sliding motion

It depends on which surface is moving

Question 23

Convex moving on Concave

Answer 23

Rolling and sliding are in the OPPOSITE direction

Question 24

Concave moving on Convex

Answer 24

Rolling and sliding are in the SAME direction

Question 25

Passive tension-

Answer 25

helps joint stability and reduces passive accessory movement Taut pubofemoral Ligament From Extension and abduction Taut ischiofemoral Ligament From extension and internal rotation Taut iliofemoral Ligament from extension

Question 26

Line of gravity (LOG)

Answer 26

causes extensor torque, counterbalanced by passive flexor torque of hip ligaments

Question 27

Close-packed vs. Loose-packed position

Answer 27

A joint is most stable at its close-packed position A joint is most mobile at its loose-packed position Joint stability can also be achieved by active muscle forces

Question 28

The close-packed position is when

Answer 28

Articulating surfaces are maximally congruent Ligaments or capsule are pulled tight (passive tension)

Question 29

Impact of forces on the MSK system

Answer 29

A force that acts on the body is referred to as a load Forces or loads that fixate or stabilize the body can also deform or injure the body

Question 30

Open chain movement

Answer 30

The prime mover is usually muscle force Decreased co-activation of antagonist muscles

Question 31

Closed chain movement

Answer 31

The prime mover is gravity when the body is moving toward the Earth The prime mover is when the body is moving away from the Earth is often defined in terms of muscle groups Increased co-activation or eccentric activation of antagonist muscles Increased loading on the joint

Question 32

Kinetics

Answer 32

describes the effect of forces on the body (force – a push or pull that can start, stop, or modify movement)

Question 33

Newton’s 1st law of motion

Answer 33

(sumF = 0) A body remains at rest or in constant linear or angular velocity except when compelled by an external force to change its state Objects in equilibrium....for example, consider a hockey puck resting on ice; the forces are (=) After the puck is struck, it is accelerated and will again be in equilibrium until another force acts on it

Question 34

Newton’s 2nd law of motion

Answer 34

quantity of the force is = to the product of the mass that received the force and the acceleration of the mass F = ma the acceleration of a body is proportionate to the magnitude of the resultant forces (F) on it and inversely proportionate to the mass (m) of the body

Question 35

Unit of force is a

Answer 35

(N) 1N= 1kgX 1m/sec2

Question 36

Newton’s third law of motion

Answer 36

action and reaction For every action force there is an = and opposite reaction force The state of motion of a body depends on the forces acting on that body (vs the forces it may exert on other bodies) Walking up slippery icy driveway

Question 37

External force: Gravity (concept of COG)

Answer 37

Center of mass – point in every body or object about which the mass is evenly distributed Human body COM is just anterior to S2 when standing Gravity acts on the center of mass of the body segment or an object When subjected to gravity, the COM is referred to as the COG (weight is the effect of the acceleration of gravity on a mass – (Wt=m*G)

Question 38

Center of mass (COM)

Answer 38

During movement, the COM is continually changing The location being a function of the size and location of the individual body segments

Question 39

Concept of COG

Answer 39

The direction of the external force due to gravity is referred to as the line of gravity (LOG)

Question 40

Forces can stabilize joints and body

Answer 40

Newton’s 1st law of motion (sumF = 0)

Question 41

Forces can produce body motion

Answer 41

Newton’s 2nd law of motion (sumF = ma)

Question 42

Action and reaction

Answer 42

Newton’s 3rd law of motion Internal and external forces counterbalance each other to: control body movement (sumF=Fi+Fe=ma) maintain stability (sumF=Fi+Fe=0)

Question 43

Each force (internal and external) is depicted by an arrow that represents a vector

Answer 43

Vector is described by its: > Magnitude > Direction (commonly referred to as the line of force and line of gravity) > Sense (indicated by arrowhead) depicting whether the force is acting upward (positive) or downward (negative) > Point of application of the force

Question 44

Torque

Answer 44

rotatory equivalent of force Product of the force x perpendicular distance (d) from the line of action to the axis of motion. So, (τorque =F * d) Forces acting a distance from the axis of rotation will produce rotation at the joint Moment arm Torque = Force x moment arm Force pushes/pulls in a linear fashion, torque rotates an object about an axis

Question 45

Moment arm

Answer 45

the shortest distance from the force vector to the axis of rotation Internal moment arm (IMA) External moment arm (EMA)

Question 46

Levers

Answer 46

Simple machine consisting of a rod suspended across a pivot point Converts force into torque Leverage describes the relative moment arm (MA) possessed by a particular force; the longer the MA, the greater the leverage

Question 47

Musculoskeletal Levers

Answer 47

Internal and external forces produce torques through a system of bony levers Internal and external torques counterbalance each other to produce motion or to achieve stability of these levers Motion: sumT = Ti + Te = Iα (angular acceleration) Newtons second law Stability: sumT = Ti + Te = 0

Question 48

3 classes of levers

Answer 48

1st class levers can have a MechAdv =, <, or > than 1 2nd class levers always have an MechAdv> than 1 3rd class levers always have an MechAdv <1

Question 49

Mechanical advantage

Answer 49

(Mech Adv) of msk lever is defined as the ratio of the Internal moment arm (IMA) to the length of the External moment arm (EMA)