Lecture 2

Question 1

Creep

Answer 1

Gradual deformation (strain) of a tissue over time as the tissue is subjected to a constant load (stress)

Question 2

Stress Relaxation

Answer 2

Reduction of a stress within a tissue over time as the tissue is subjected to a constant deformation (strain)

Question 3

Strain

Answer 3

A deformation of tissue; the change of length in respect to the original length. To figure out the percent, find the difference between the original and the result and divide by the original.

Question 4

Stress

Answer 4

Force over an area (pressure), often applied to biological tissue

Question 5

Elastic Region of Stress/Strain Curve

Answer 5

The region in which a tissue will go back to its original length when the stress is removed.

Question 6

Yield Point of Stress/Strain Curve

Answer 6

The point at which the Plastic Region is entered.

Question 7

Plastic Region of Stress/Strain Curve

Answer 7

The tissue does not go back to its original length when the stress is removed. It is permanently stressed.

Question 8

Modulus in Elasticity

Answer 8

(Change in stress)/(Change in strain)

Question 9

In compression, is bone strongest, medium strength, or weakest?

Answer 9

Strongest

Question 10

In tension, is bone strongest, medium strength, or weakest?

Answer 10

Medium strength

Question 11

In shear force, is bone strongest, medium strength, or weakest?

Answer 11

Weakest

Question 12

What type of exercise is the best for healthy bones?

Answer 12

Weight bearing exercise

Question 13

Osteoporosis

Answer 13

Bone becomes more porous (less dense); this is seen in both men & women & especially in the elderly.

Question 14

Crimp in Tendon

Answer 14

Bit of waviness in tendon when it is relaxed. This waviness disappears when you first start to put stress on the tendon, happens in the Toe Region of the stress/strain curve.

Question 15

Are ligaments elastic?

Answer 15

No. Once they are stretched, they are stretched. This leaves you more prone to injuries.

Question 16

Muscles can help to stabilize joints, but…

Answer 16

They will fatigue and the risk of injury will increase.

Question 17

Immobilization decreases what?

Answer 17

Strength

Question 18

ACL Rehabilitation usually takes how much time?

Answer 18

6-12 months

Question 19

Avascular

Answer 19

Poor healing capacity

Question 20

Aneural

Answer 20

No pain

Question 21

How much of the net weight of cartilage is water?

Answer 21

70-85%

Question 22

Boundary Lubrication

Answer 22

Load bearing surfaces separated by lubricin molecules (most effective during low joint loading)

Question 23

Fluid Film

Answer 23

Load bearing surfaces separated by film of lubricate maintained under pressure. Compression causes cartilage to deform & “weep” fluid, which forms fluid film of separation over weight bearing surfaces, inhibiting surface to surface contact. When load subsides, fluid flows back into cartilage. Most effective during high joint loading.

Question 24

Friction Force

Answer 24

Normal force times coefficient of friction (how rough or smooth something is)

Question 25

Cartilage is most permeable during...

Answer 25

Low stress

Question 26

Joint loading increases...

Answer 26

Pressure within cartilage and a noncommitant increase in tension in collagen fibers.

Question 27

Thixotropic

Answer 27

Viscosity varies inversely with joint velocity and temp. Describes synovial fluid.

Question 28

Moment Arm

Answer 28

Perpendicular to the Line of Force at the COM and extends to the axis of rotation.

Question 29

Mechanical Advantage

Answer 29

(Internal Moment Arm)/(External Moment Arm)