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Musculokeletal Phyt I > Week 2 - Lecture 1 - Tissue Mechanics and Injury > Flashcards

Week 2 - Lecture 1 - Tissue Mechanics and Injury Flashcards

1
Q

Explain why the human body must adapt in appearance and composition in response to functional demand. How can these demands change?

A

• Our musculoskeletal systems must adapt in appearance and composition in
response to functional demand
• These demands can change with immobilization, inactivity, or training
• Understanding the functional demands and the tissues’ response, we can modify
the stresses on joint structure during rehabilitation to optimize function

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2
Q

What are tissues (definition)?

What are the four different types of tissue?

A

• An aggregate of cells that
have similar structure and
function

  1. Connective tissue
  2. Epithelial tissue
  3. Muscle tissue
  4. Nervous tissue
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3
Q

What are various examples of connective (inert) tissue?

A
  • All joints in the body are composed of connective tissue
  • Bones
  • Bursae
  • Capsules
  • Cartilage
  • Discs
  • Menisci
  • Ligaments
  • Tendons
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4
Q

How do you go from a tissue to a full multi-cellular organism? How do the cells get together, coordinate, structure themselves to form me or you?

A

And the answer is, or at least it involves, something called the extracellular matrix.

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5
Q

What are the different non-fibrous components of the ECM?

A

Non-fibrous component
• Glycoproteins
• Proteoglycans

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6
Q

What are the functions of the ECM?• Attracting and binding water
• Supporting substance for fibrous and
cellular components
• Contributes to overall strength of
connective tissue thereby protecting it

A

• Attracting and binding water
• Supporting substance for fibrous and
cellular components
• Contributes to overall strength of
connective tissue thereby protecting it

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7
Q

What are the different fibrous components of the ECM?

A

• Fibrous Component
• Collagen – white fibrous, steel-like
strength, rigid
• Elastin – yellow fibrous, elastic properties

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8
Q

What is the difference between Collagen type 1 to collagen type 2.

A

Collagen type 1: thick fibers, little elongation
• Resists tensile forces well
• Collagen type 2: thinner, less stiff fibers
• Resists compression and shear

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9
Q

What are Resident cells?

What are circulating cells?

A

Resident Cells – Always present but depends on tissue

  • Fibroblasts (collagen)
  • Osteoblasts (bone)
  • Chondroblasts (cartilage)

Circulating Cells – If inflamed or damaged

  • Lymphocytes
  • Macrophages
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10
Q

Explain the concept of a ligament.

A

BONE TO BONE

• Cells make up 10-20%
• ECM makes up 80-90%
• Primarily composed of type I collagen fibrils that are
densely packed into fiber bundles arranged in line
with the applied tensile force
• Depending on the ligament there may be varying
directions of tensile force therefore ligaments run in
multiple directions (e.g., MCL)

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11
Q

Explain the concept of a tendon.

A

BONE TO MUSCLE

Similar make up as ligaments
• More type I collagen thought to be an adaptation
to larger tensile forces
• Primarily aligned in one direction

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12
Q

What is a fibrocartilaginous junction?

A
  • The gradual change in tendon structure, divided into four zones
  • Diffuses the load at the tissue-bone, interface, perhaps to help prevent injury
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13
Q

What is the musculotendinous junction?

A

• Muscle cells intertwine with the tendon
• Very sensitive to mechanical conditions
and becomes flatter with low load
• Weakens the junction increasing
susceptibility to injury
• Loading caution post-immobilization

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14
Q

What is hyaline cartilage?

A

• Lines articulating bones and distinguishes synovial joints
• Type II collagen throughout the ECM and compresses on the proteoglycan (PG)
molecules that hold onto water during load
• Articular cartilage has much more PG than other joint structures
• Limited blood supply, nutrient diffusion with compression

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15
Q

What is articular cartilage and the different zones?

A

• Zone 1: parallel fibers,
smooth, reduced friction,
distribute forces
• Zone 2: mesh-like to hold
water, absorbs
compression
• Zone 3: perpendicular,
securely holds the
calcified cartilage

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16
Q

What is fibrocartilage?

A

• Type I > type II collagen
• Collagen density to keep the water in the tissue (versus hyaline cartilage that
utilizes collagen and chemical water attraction)
• Limited blood supply, nutrient diffusion with compression
• E.g., meniscus
• Circumferential fibers (deep zone)
• Radial fibers (superficial zone)

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17
Q

Explain the components of the bone.

A
  • Primarily type I collagen
  • Mineral (Ca2+)
  • Two layers:
  • Cancellous (spongy)
  • Compact (cortical)

• Osteoblasts versus osteoclasts

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18
Q

What are some of the behavioural properties?

A

Structural Properties
• Load, force and elongation
• Stress and Strain
Viscoelasticity
Time/Rate-Dependent Properties
• Creep
• Stress Relaxation
• Strain Rate Sensitivity

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19
Q

Explain the slope of the different lines… What do they represent.

A

The slope of the line represents the stiffness and compliance of the tissue
• Steep curve: high stiffness, low compliance
• Gradual curve: low stiffness, high compliance

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20
Q

What are the 5 different structural properties?

A
  1. Tensile strain
  2. Bending strain
  3. Torsional loading
  4. Shear loading
  5. Compressive strain
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21
Q

What is viscoelasticity?

A

• Elasticity: returning to the original length or shape of the material after the load
has been removed
• Also known as deformation (proportional to the amount of force)
• Elastic tissue: return to resting length when force is removed
• Viscosity: the material’s resistance to flow
• Force applied to viscous material display time/rate dependent properties
• Viscous tissue: creeps under constant load (plastic does not return shape)

22
Q
A
23
Q

What are the 3 time/rate dependant properties?

A

• Creep: continuous change in shape with prolonged force application
• Stress Relaxation: a tissue is stretched to a fixed length and held constant, the
force needed to maintain that length reduces over time
• Strain-Rate Sensitivity: more force is required to deform a tissue rapidly versus
slowly

24
Q

What are some important facts about bone?

A
  • Cortical bone withstands greater force with less deformation than cancellous bone
  • Greater compression versus tension
  • The amount of strain required to reach failure (fracture) is less in cortical bone
  • Frequent loading of low magnitude: stress fracture
  • Single load of high magnitude: complete failure (fracture)
25
Q

Types of fractures.

A
26
Q

Explain the aspects of a tendon.

A

Differences in stress-strain reflects varied proportion of collagen and type
• Cross-sectional area, material and tendon length determine the amount of force
that a tendon can resist and the amount of elongation that it can undergo
• Continuous compression modifies composition to resemble cartilage (reducing
tensile strength)
• Tensile loads over long periods will increase tissue size, collagen concentration
and cross-linking

27
Q

Explain the contents of a ligament.

A

Differences in stress-strain reflects varied proportion of collagen and type
• Similar mechanics to tendons
• Increased thickness and strength with intermittent tensile loads
• Slightly less resistant to tensile stress than tendons because they must be oriented
in multiple directions (but withstand a wider variety of force directions)

28
Q

Cartilage is to resist load:

A

• To resist load
1. Stress developed in the fibrillar portion of ECM
2. Swelling pressures developed in the interstitial fluid
3. Frictional drag resulting from fluid flow through the ECM
• Compression reduces volume and increases pressure to push fluid out (rapid initial
deformation becoming gradual and stops)
• Varied orientation of fibers through zones creates non-linear behaviour

29
Q

• Thousands of fibers grouped into:
1.

2.

3.
• Myofilaments:

1.

2.

3.
• Cross-bridge:

___________________

A

• Thousands of fibers grouped into:
• Fascicles
• Myofibrils
• Myofilaments
• Myofilaments: actin, myosin, troponin
• Cross-bridge: Action potential releases Ca2+ to
expose binding sites between actin and myosin

30
Q

Explain the cross-bridge cycle.

A
31
Q

What is a sarcomere?

• (I) only ______“___________”, (A) ______________ “____________”, (H) only _____________

A

• (I) only actin “isotropic”, (A) actin and myosin “anisotropic”, (H) only myosin

32
Q

Explain these different positions of the sarcomere.

  1. Resting
  2. Concentric
  3. Eccentric
  4. Isometric
A

Resting (inactive)
Concentric (shortening)
Eccentric (lengthening)
Isometric (active)

33
Q

ACTIVE TENSION
• Developed by the active contractile elements of the muscle
• Depends on more cross-bridges being formed, by:
•
•
•
•

A

ACTIVE TENSION
• Developed by the active contractile elements of the muscle
• Depends on more cross-bridges being formed, by:
• Frequency of motor unit firing
• Number of motor units firing
• Size of motor units firing
• Diameter of the axon in motor unit (conduction velocity)

34
Q

Explain passive tension.

A

• Tension developed by passive, non-contractile components of muscle
• Parallel elastic components
• When the muscle is stretched they resist and contribute to the tension (only
in tension stretch not shortening)
• Epimysium
• Perimysium
• Endomysium
• Series elastic component
• Tendon (stretch exerts a pull on the tendon)

35
Q

MUSCLE TENSION

Direct relationship between _______________and ____________
• Optimal length: ________________________________
• As a muscle is lengthened or
shortened from the optimal length, the
amount of tension generated is
__________________

A

MUSCLE TENSION

Direct relationship between tension
development and muscle length
• Optimal length: capable of developing
a maximal tension
• As a muscle is lengthened or
shortened from the optimal length, the
amount of tension generated is
diminished

36
Q

What happens to the muscle tension when the muscle is being pulled apart?

Explain also with a graph.

A

When the muscle is being pulled apart,
increase stretch
• Passive increases while active
decreases, but the overall tension
increases as the muscle gets longer

37
Q
A
38
Q

Name a few tissue modifiers.

A
  • Age
  • Immobility
  • Disuse
  • Injury
  • Medication
  • Pain
39
Q

CONTRACTILE STRUCTURES
• Muscle, tendon, tendon-periosteal (TP) junction
• Pain increases with ____________ movements
• In the _________ direction
• Pain increases with ____________ movements
• In the ____________ direction
• E.g., painful active and resisted elbow flexion, and passive elbow extension

A

CONTRACTILE STRUCTURES
• Muscle, tendon, tendon-periosteal (TP) junction
• Pain increases with ACTIVE AND RESISTED movements
• In the SAME direction
• Pain increases with PASSIVE movements
• In the OPPOSITE direction
• E.g., painful active and resisted elbow flexion, and passive elbow extension

40
Q

INERT STRUCTURES
• Ligaments, bursae, fascia, nerve roots, capsules, dura mater
• Non-contractile
• Pain is provoked by ________________
• Pain increases with _____________________ movements (often end-range)
• In the _____________ direction
• Resisted movements are not painful

A
  • Ligaments, bursae, fascia, nerve roots, capsules, dura mater
  • Non-contractile
  • Pain is provoked by stretching the tissue
  • Pain increases with ACTIVE AND PASSIVE movements (often end-range)
  • In the SAME direction
  • Resisted movements are not painful
41
Q

What are passive movements?

A
  • Physiological movements are used (PPM)
  • Need full accessory movements for PPM to occur (movements beyond control)
  • E.g., Bend finger – interphalangeal flexion plus slide
  • Apply over-pressure (OP) at the end to determine end-feel
  • Isometric muscle testing (strong, weak, painful, painless) – compared other side
  • To determine tissue type (source of pain)
  • Treatment guided by tissue and the specific lesion
42
Q

What are end-feels?

A

• A sensation that the therapist feels in the joint and tissues at the end of available
range of motion during passive movement
• May be normal or pathological (abnormal)
• Must compare the affected and unaffected sides

43
Q
A
44
Q

What are normal end feels?

A

Bone to Bone
• Abrupt stop in motion; two bone surfaces coming together (e.g., elbow ext)
Capsular or Soft Tissue Stretch
• Hard-ish stop in motion; spring or slight give (e.g., shoulder lateral rotation)
Soft Tissue Approximation
• Squishy, giving
• Movement stopped by limb hitting again soft tissue of another body part
• e.g., knee flexion

45
Q

What are the different abnormal end feels?

A

Empty – movement stopped by pain before resistance is felt (e.g., 10/10 pain)
Spasm – involuntary, vibrant twang (e.g., recent #)
Springy Block – unexpected rebound, non-capsular pattern restriction (e.g., tear)
Abnormal Bone to Bone – early abrupt stop, crepitus or grating (e.g., post immobilization)
Abnormal Capsular – early hard-ish stop before end range (e.g., frozen shoulder)

46
Q

What is a capsular pattern of restriction?

A

A characteristic pattern of expected proportional limitation of movement, specific
to a particular joint
• Exists only in those joints controlled by muscle, which have a joint capsule and
are lined by a synovial membrane
• Suggests that the entire capsule and/or synovial membrane of the joint is involved
• Total joint reaction (e.g., post-immobilization)
• Determined by passive movements

47
Q

Define a closed packed position (CPP) for articular joint positions.

A

Most stable position
• Greatest protection for the joint
• Usually avoided during assessment
• Greatest congruency of surfaces
• Capsule, ligaments under max tension
• If swollen, CPP cannot be reached

48
Q
A
49
Q

Define a loose packed position (LPP) for articular joint positions.

A
  • Any position other than CPP
  • Not congruent
  • Capsule and ligaments are relaxed
  • Greatest room for swelling
  • Naturally adopted for rest when painful
  • Least amount of stress on structures
50
Q

What is the resting position?

A
  • A specific loose packed position
  • Minimal congruency between surfaces
  • Capsule and ligament have greatest laxity
  • Passive separation of joint surfaces, therefore greatest swelling
  • Usually the mid-position for the joint
51
Q

What is the constant length phenomenon?

A

Limitation of movement at one joint is dependent on the position at which another
joint is held
• Restricting tissue is outside the joint
• Suggests a lesion in a tissue that spans two joints
E.g., lumbar disc lesion, irritates the sciatic nerve à positive SLR
E.g., muscle adhesion in the two joint muscle

Musculokeletal Phyt I (5 decks)

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