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Biomechanics Winter 2024 > Joints & Muscles > Flashcards

Joints & Muscles Flashcards

1
Q

What can synovial joints be classified into?

A
  • ovoid
  • saddle
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2
Q

Describe an ovoid synovial joint

A
  • most joints
  • more of an egg shape
  • paired mating surfaces that are imperfectly spherical
  • 1 concave, 1 convex
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3
Q

Describe a saddle synovial joint

A
  • paired convex and concave surfaces
  • oriented at 90 degrees to each other
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4
Q

What are synarthrodial synovial joints?

A
  • fibrous and cartilaginous joints
  • more stable, not as much movement
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5
Q

What are diarthrodial synovial joints?

A
  • has joint capsule with synovial fluid
  • more for joint mobility
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6
Q

What are examples of uniaxial, diaxial, triaxial, and non-axial joints?

A
  • Uniaxial: hinge, pivot
  • biaxial: saddle, chodiloid
  • triaxial: ball & socket
  • non-axial: slide on each other but don’t move (i.e. facet joints in spine, carpal joints)
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7
Q

List the 7 elements ALWAYS associated with synovial joints

A
  • synovial fluid
  • articular cartilage
  • joint capsule
  • synovial membrane
  • ligaments
  • blood vessels
  • sensory nerves
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8
Q

What are some elements sometimes associated with synovial joints

A
  • intra-articular discs/menisci
  • peripheral labrum
  • fat pads
  • bursa
  • synovial plicae
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9
Q

What is the importance of water to ground substance?

A
  • provides a medium for nutrient diffusion
  • aids in resilience
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10
Q

What is periarticular cartilage made of?

A
  • fibrous proteins (collagen, elastin)
  • ground substance (GAGs, water, solutes)
  • cells (fibroblasts, chondrocytes)
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11
Q

What are the two types of collagen?

A

Type 1:
- thick, stiff, strong
- ligaments, capsules, tendons

Type 2:
- thin, internal strength
- hyaline cartilage

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12
Q

What is elastin?

A
  • resists stretching; more give
  • elastic and hyaline cartilage; ligamentum flavum
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13
Q

For ligaments describe:
1)category of connective tissue
2) composed of
3) potential for healing
4) sense pain or proprioception?
5) function/purpose
6) best stimuli for rehab

A

1) dense regular connective tissue
2) ground substance, fibroblasts, type 1 collagen
3) limited blood supply (poor healing)
4) can feel pain (maybe proprioception)
5) bone to bone (stability)
6) stress in direction aligning w/ normal stresses in everyday life; gradual loading, iso’s

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14
Q

For tendons describe:
1)category of connective tissue
2) composed of
3) potential for healing
4) sense pain or proprioception?
5) function/purpose
6) best stimuli for rehab

A

1) Dense regular connective tissue
2) type 1 collagen, proteoglycans (low-moderate)
3) limited blood supply (but better than ligaments)
4) can feel pain & proprioception
5) muscle to bone (force production)
6) tensile stress, gradual loading, iso’s

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15
Q

For joint capsule describe:
1)category of connective tissue
2) composed of
3) potential for healing
4) sense pain or proprioception?
5) function/purpose
6) best stimuli for rehab

A

1) Dense irregular connective tissue
2) type 1 collagen, ground substance, chondrocytes, BV’s, nerves
3) can heal
4) sense pain and proprioception
5) nutrition, mobility
6) motion, PROM, AROM

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16
Q

For articular cartilage describe:
1)category of connective tissue
2) composed of
3) potential for healing
4) sense pain or proprioception?
5) function/purpose
6) best stimuli for rehab

A

1) hyaline cartilage
2) type 2 cartilage, ground substance, chondrocytes
3) hard to heal (avascular; nutrients from synovial fluid)
4) can’t feel (aneural)
5) disperse compressive forces to subchondral bone & reduce friction b/w joint surfaces
6) general motion, proceed to intermittent compression

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17
Q

For fibrocartilage describe:
1)category of connective tissue
2) composed of
3) potential for healing
4) sense pain or proprioception?
5) function/purpose
6) best stimuli for rehab

A

1) Dense connective tissue and articular cartilage
2) type 1 collagen, moderate proteoglycans, chondrocytes/fibroblasts
3) limited blood supply (outer 1/3rd vascularized; hard to heal)
4) can’t feel (aneural; outer 1/3rd innervated)
5) support & stabilize joint, guide arthrokinematics, dissipate forces (meniscus, labrum, IV discs)
6) general motion, progress to intermittent compression

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18
Q

For bone describe:
1)category of connective tissue
2) composed of
3) potential for healing
4) sense pain or proprioception?
5) function/purpose
6) best stimuli for rehab

A

1) bone
2) osteoblasts, osteoclasts
3) great healing (very vascularized)
4) feels pain (maybe proprioception; very innervated; pressure & pain)
5) rigids support to body; provides muscles a system of levers
6) weight-bearing, gradual loading

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19
Q

How does articular cartilage get nutrition?

A
  • from synovial fluid moving inside the joints
  • PT’s can do this via PROM
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20
Q

Explain Wolff’s Law

A
  • bone is laid down in areas of high stress & reabsorbed in areas of low stress
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21
Q

How long does it take bone, ligaments/tendons/joint capsules, and articular cartilage to heal?

A

Bone: 6-8 weeks

Ligament: 3-6 months (remodeling); 12-18 months (full recovery)

Tendon: mild sprain 2-4 weeks; moderate sprain <10wks

joint capsule: at least 6 wks

Articular cartilage: may never heal -> turns/grows to fibrocartilage; can take 6-12 months

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22
Q

What is the difference between acute and chronic trauma?

A

Acute
- one single, overwhelming event
- produces detectable pathology
- creates cytokines

Chronic
- accumulation of lesser injuries over extended period of time
- “microtrauma”
- for articular cartilage + fibrocartilage: lose proteoglycans = less resilience

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23
Q

What is the difference between dislocation and subluxation?

A

Dislocation:
- complete disassociation

Subluxation:
- partial disassociated

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24
Q

How long & what happens during each phase of healing?

A

Inflammation:
- less than 1 week
- increased local blood supply
- inflammatory cells & leukocytes

Repair:
- about 3 weeks
- cells proliferate, fibers need to be realigned
- collagen & GAGs replacing damaged tissue
- damaged nerve endings/capillaries sprouting

Remodeling
- about 3 weeks to 6 months
- scar tissue needs to be stressed along lines of force it encounters normally
- turning weak scar tissue to functioning tissue
- low load, regular, intermittent loading for 3 months to a year or more

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25
Q

What happens if a therapist is too aggressive during the repair phase?

A
  • repair phase can be elongated
  • inflammatory chemicals/exudate can become present
  • fibers are not oriented correctly yet so strength is not present
  • could injure tissue more
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26
Q

What happens if the remodeling process is not carried out properly?

A
  • pain and limited function could occur
  • tissue will remain weak & prone to injury
  • nerves will cause pain if scar is stretched or loaded
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27
Q

How does immobilization or disuse affect ligaments?

A
  • decreased collagen content = weakness
  • decreased cross-linking = weakness
  • leads to 50% less strength quickly
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28
Q

How does immobilization or disuse affect tendons?

A
  • decreases collagen content = weakness
  • muscle weakness/atrophy
  • interdigitation junction loss = weakness
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29
Q

How does immobilization or disuse affect joint capsules?

A
  • shortening of joint capsules = increased resistance to movement
  • loose-packed position (relaxes to this position making normal ROM difficult)
  • adhesions in synovial folds
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30
Q

How does immobilization or disuse affect articular cartilage?

A
  • thinning & degradation, atrophy, softening
  • 42% increase in deformation under compression
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31
Q

How does immobilization or disuse affect bone?

A
  • decreased bone mineral content
  • regional osteoporosis
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32
Q

What is important for tendon and ligament strength?

A
  • gradual loading
  • motion is lotion
  • tensile loading
33
Q

What are some strategies to minimize immobilization consequences?

A
  • CPM machines
  • decrease duration of immobilization
  • dynamic splinting devices
  • graded loading after immobilization
  • increase recovery period to months instead of days/weeks
34
Q

How are the effects of aging similar to immobilization or disuse?

A
  • decreased repair capabilities
  • dehydrated articular cartilage
  • ligaments develop weakness & adhesions
  • tendons lose stiffness so muscles can’t stabilize joints as well
  • bone metabolism slows down
35
Q

What types of loads are appropriate for rehab with the connective tissues mentioned so far?

A

Ligaments:
- tensile loads
- SL pistol squat from box

Tendon:
- tensile loads
- calf raises
- progressive loading

Cartilage:
- low frequency compression loads
- “milking action”
- low load repetitive compression
- recumbent bike

Fibrocartilage:
- high magnitude/sustained loading

Bone:
- high frequency
- running, jumping
- weight bearing

36
Q

Explain the vicious cycle of joint dysfunction

A
  • when a joint is not free to move, the muscles that move it cannot be free to move
  • muscles cannot be restored to normal if the joints are not free to move
  • Normal muscle function is dependent on normal joint movement
  • impaired muscle function perpetuates & may cause deterioration in abnormal joints
37
Q

Describe the structural organization of skeletal muscle from most superficial to deep

A

muscle belly (epimysium) -> fascicles (perimysium) -> fiber/muscle cells (endomysium) -> myofibril -> myofilaments -> contractile proteins (actin & myosin) + non-contractile proteins (titin & desmin)

38
Q

What is the difference between series and parallel elastic components and their significance in muscle tissue?

A

Series:
- connected in series
- tendon on each end of the muscle (titin, tendons)

Parallel:
- surround/or parallel w/ contractile proteins
- extracellular connective tissue (perimysium)

Stretching of the muscle at each joint stretches both components
- creates a springness & stiffness in the muscle

39
Q

What is a sarcomere?

A

fundamental active force generator

40
Q

Explain the sliding filament hypothesis

A

Myosin & actin filaments form cross bridges
- once cross bridges form, actin slides past myosin heads generating force that pulls z-discs closer together
- myosin “grab & pull” actin together called the power stroke

41
Q

What is the relationship between cross bridge formation & fiber length to force production?

A
  • more cross-bridge formations results in more force produced
  • fiber length is important for creating more cross bridges
42
Q

How does a motor unit work?

A
  • alpha motor neuron & structures/fibers it innervates
  • Efferent signals leave ventral horn of spinal cord to innervate structures
43
Q

Explain Type I muscle fiber

A
  • slow twitch
  • slow oxidative
  • tonic
  • red
  • fatigue resistant
    EX: soleus
44
Q

Explain Type IIa muscle fiber

A
  • intermediate
  • fast fatigue resistant
  • Fast oxidative glycolytic
45
Q

Explain Type IIb/x muscle fiber

A
  • fast twitch
  • fast glycolytic
  • phasic
  • white
  • fatigue fast
    EX: gastrocnemius
46
Q

How does recruitment differ from rate coding?

A

Recruitment:
- initial activation of motor neurons
- order how motor neurons are activated
- smaller units then larger units if needed

Rate of coding:
- has to do with the rate of firing of action potentials in a muscle
- controls/fine tunes the force produced by muscles
- tetanus

47
Q

What is the difference between fused and unfused tetanus?

A

fused: stable muscle contraction
- greatest force level possible

unfused: set of repeating AP’s that excites a muscle fiber before relaxation after the previous twitch

48
Q

Explain Henneman’s size principle

A

smaller motor units are recruited first then larger ones are recruited if needed

  • small = fine motor/small forces
  • large = large movements/large forces
49
Q

Why are EMG readings distributed during motion?

A

readings from other muscles during movement can affect EMG
- could read higher because of other muscle activations

50
Q

How do physiological cross-sectional area and pennation angle affect muscle force production?

A

thicker muscle = greater force

Pennation angle:
- angle of orientation between muscle fiber and tendon orientation
- 0 degrees = muscle fibers parallel with tendon (ALL force goes through tendon)
- greater than 0 = muscle fibers oriented oblique/perpendicular to tendon (SOME force goes through tendon)

pennate muscles generate more force b/c of more PCSA

51
Q

Explain the difference between isometric, concentric, and eccentric

A

Isometric:
- increased force with not increase/decrease in muscle length
-IT=ET

Concentric:
- muscle shortening
- IT>ET

Eccentric:
- muscle lengthening as its contracting
- IT<ET
- controlled lowering

52
Q

How does recruitment of motor units differ between concentric and eccentric activation?

A

ECC:
- less motor units recruited

CONC:
- more motor units needed to be recruited to produce same force

53
Q

Explain the difference between “Isotonic”, “plyometric”, and “Isokinetic”

A

Isotonic:
- equal tension
- both conc & ecc
- muscle tension just changes throughout movement

Plyometrics:
- muscle tendon complex is stretched before forceful contraction
- helps produce better force
- tendons stretch

Isokinetic:
- same speed throughout ROM
- resistance directly proportional to muscle torque
- measures torque output
- BIODEX

54
Q

What does reciprocal inhibition mean?

A
  • antagonist is inhibited while agonist is working
55
Q

Explain the passive length tension curve

A
  • moving/stabilizing joint against gravity
  • tension developed in non-contractile components of a muscle
  • parallel & series elastic
  • critical length = where all non-contractile tissue brought to initial level of tension
  • tension continues after this critical length
56
Q

Explain the active length tension curve

A
  • tension developed by contractile fibers of the muscle
  • optimal length = resting length
  • greatest isometric force
  • greatest cross-bridges available/form
57
Q

Explain the total length tension curve

A
  • active tension added to the passive tension
  • passive tension provides the tension beyond normal resting length
  • active tension provides tension before normal resting length
58
Q

How do the cross-bridges in the sarcomere affect active tension?

A
  • greater cross bridges available = greater force production = more active tension
59
Q

What is the difference between passive and active insufficiency?

A

Passive:
- muscle length is limited by the crossing of another joint
- EX: hip flexion is limited with straight leg due to hamstrings

Active:
- happens with joints crossing multiple joints
- less cross bridges are available
- EX: less force produced with finger flexion when wrist is flexed compared to wrist slightly extended

60
Q

How does tenodesis differ from passive insufficiency?

A

tenodesis is passive movements of joints due to muscle/tendon crossing that joint
- tenodesis allows other joints to move passively while passive insufficiency inhibits a joints ability to move
- EX: fingers flex when wrist EXT & EXT when wrist is flexed

61
Q

What is the significance of a muscles resting length?

A
  • this length provides the greatest length for force production
  • greatest amount of cross-bridges are available to form
  • greatest isometric force
62
Q

Describe the difference in Conc & Ecc activation as it relates to force-velocity relationship

A

Concentric:
- faster shortening = less force (less cross-bridges are formed; slide past too fast)
- slower shortening = more force
- increase weight = decreased velocity

Eccentric:
- faster lengthening = more force
- slower lengthening = less force
- more weight= increased velocity

63
Q

How does hypertrophy of muscle occur during strength training?

A
  • increased protein synthesis within muscle fibers
  • adds sarcomeres in parallel with muscle fiber
  • series component increase = speed of contraction
    BEST in type II fibers

usually takes about 6 weeks of consistent training

64
Q

What are general guidelines for training healthy muscle at high-intensity?

A
  • progressive increase in magnitude of the load (3-12 reps)
  • 3 x 3-12
65
Q

What are general guidelines for training healthy muscle at low-intensity?

A
  • lifting lighter load to at least 15 reps max
  • 3 x 15
66
Q

What are the 7 factors the affect muscle performance?

A
  • location (type of joint determines motion)
  • number of joints (single vs multi-joint)
  • strength training
  • muscle fatigue
  • reduced use, disuse, immobilization
  • aging
  • injury (overuse = chronic; strain = acute)
67
Q

What is the greatest muscle contraction for scar tissue remodeling?

A
  • eccentric contractions
68
Q

How does fatigue relate to force production?

A
  • with increased fatigue there is decreased force production
  • with increased force production = increased rate of fatigue
69
Q

How does fatigue relate to recruitment of motor units?

A
  • increased fatigue = increased recruitment of larger motor units
70
Q

How does fatigue relate to muscle fiber type?

A

Type 1:
- fatigued by low-intensity, long duration
- longer rest time

Type 2:
- fatigued by high-intensity, short duration
- shorter rest time

71
Q

How does fatigue relate to types of muscle activations?

A

Concentric:
- more fatiguing

Eccentric:
- less fatiguing
- leads to DOMS

72
Q

What is DOMS?

A

Delayed onset muscle soreness
- this is a strain related injury to the forcefully stretched muscle during ECC training

73
Q

What happens to a muscle with reduced use?

A
  • atrophy
  • loss in strength
  • reduced protein synthesis
  • increased number of type 1 fibers with immobilization
74
Q

What happens to a muscle if immobilized in a shortened position?

A
  • decreased sarcomeres which adapts the length-tension relationship to shortened position
  • thickening of perimysium & endomysium
  • circumferential collagen fibril orientation
  • connective tissue > muscle tissue
  • muscle weight loss & atrophy
  • stiffness, resistance to stretch
  • loss of strength is greatest in shortened position
75
Q

What happens if a muscle is immobilized in lengthened position?

A
  • increased sarcomere numbers BUT decreased sarcomere length
  • increased perimysium & endomysium
  • increased max tension capacity
  • passive tension is better
76
Q

What can therapists do to mitigate the effects of disuse from immobilization?

A
  • early mobilization as early as possible
  • if in cast, RIGHT when cast is off move it
77
Q

What is senile sarcopenia?

A
  • decreased number of fibers and size of those fibers (especially type II)
  • loss in muscle tissue with advanced age
78
Q

What changes occur in muscle tissue because of senile sarcopenia?

A
  • leads to increased levels of intramuscular connective tissue & fat
  • could be associated with apoptosis, diet, and activity level
  • does NOT alter plasticity of neuromuscular system

Biomechanics Winter 2024 (6 decks)

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