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Biomechanics Winter 2024 > Joints & Muscles > Flashcards

Joints & Muscles Flashcards

(78 cards)

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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
What happens if a therapist is too aggressive during the repair phase?
- 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
26
What happens if the remodeling process is not carried out properly?
- pain and limited function could occur - tissue will remain weak & prone to injury - nerves will cause pain if scar is stretched or loaded
27
How does immobilization or disuse affect ligaments?
- decreased collagen content = weakness - decreased cross-linking = weakness - leads to 50% less strength quickly
28
How does immobilization or disuse affect tendons?
- decreases collagen content = weakness - muscle weakness/atrophy - interdigitation junction loss = weakness
29
How does immobilization or disuse affect joint capsules?
- shortening of joint capsules = increased resistance to movement - loose-packed position (relaxes to this position making normal ROM difficult) - adhesions in synovial folds
30
How does immobilization or disuse affect articular cartilage?
- thinning & degradation, atrophy, softening - 42% increase in deformation under compression
31
How does immobilization or disuse affect bone?
- decreased bone mineral content - regional osteoporosis
32
What is important for tendon and ligament strength?
- gradual loading - motion is lotion - tensile loading
33
What are some strategies to minimize immobilization consequences?
- CPM machines - decrease duration of immobilization - dynamic splinting devices - graded loading after immobilization - increase recovery period to months instead of days/weeks
34
How are the effects of aging similar to immobilization or disuse?
- 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
What types of loads are appropriate for rehab with the connective tissues mentioned so far?
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
Explain the vicious cycle of joint dysfunction
- 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
Describe the structural organization of skeletal muscle from most superficial to deep
muscle belly (epimysium) -> fascicles (perimysium) -> fiber/muscle cells (endomysium) -> myofibril -> myofilaments -> contractile proteins (actin & myosin) + non-contractile proteins (titin & desmin)
38
What is the difference between series and parallel elastic components and their significance in muscle tissue?
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
What is a sarcomere?
fundamental active force generator
40
Explain the sliding filament hypothesis
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
What is the relationship between cross bridge formation & fiber length to force production?
- more cross-bridge formations results in more force produced - fiber length is important for creating more cross bridges
42
How does a motor unit work?
- alpha motor neuron & structures/fibers it innervates - Efferent signals leave ventral horn of spinal cord to innervate structures
43
Explain Type I muscle fiber
- slow twitch - slow oxidative - tonic - red - fatigue resistant EX: soleus
44
Explain Type IIa muscle fiber
- intermediate - fast fatigue resistant - Fast oxidative glycolytic
45
Explain Type IIb/x muscle fiber
- fast twitch - fast glycolytic - phasic - white - fatigue fast EX: gastrocnemius
46
How does recruitment differ from rate coding?
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
What is the difference between fused and unfused tetanus?
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
Explain Henneman's size principle
smaller motor units are recruited first then larger ones are recruited if needed - small = fine motor/small forces - large = large movements/large forces
49
Why are EMG readings distributed during motion?
readings from other muscles during movement can affect EMG - could read higher because of other muscle activations
50
How do physiological cross-sectional area and pennation angle affect muscle force production?
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
Explain the difference between isometric, concentric, and eccentric
Isometric: - increased force with not increase/decrease in muscle length -IT=ET Concentric: - muscle shortening - IT>ET Eccentric: - muscle lengthening as its contracting - IT
52
How does recruitment of motor units differ between concentric and eccentric activation?
ECC: - less motor units recruited CONC: - more motor units needed to be recruited to produce same force
53
Explain the difference between "Isotonic", "plyometric", and "Isokinetic"
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
What does reciprocal inhibition mean?
- antagonist is inhibited while agonist is working
55
Explain the passive length tension curve
- 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
Explain the active length tension curve
- tension developed by contractile fibers of the muscle - optimal length = resting length - greatest isometric force - greatest cross-bridges available/form
57
Explain the total length tension curve
- 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
How do the cross-bridges in the sarcomere affect active tension?
- greater cross bridges available = greater force production = more active tension
59
What is the difference between passive and active insufficiency?
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
How does tenodesis differ from passive insufficiency?
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
What is the significance of a muscles resting length?
- this length provides the greatest length for force production - greatest amount of cross-bridges are available to form - greatest isometric force
62
Describe the difference in Conc & Ecc activation as it relates to force-velocity relationship
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
How does hypertrophy of muscle occur during strength training?
- 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
What are general guidelines for training healthy muscle at high-intensity?
- progressive increase in magnitude of the load (3-12 reps) - 3 x 3-12
65
What are general guidelines for training healthy muscle at low-intensity?
- lifting lighter load to at least 15 reps max - 3 x 15
66
What are the 7 factors the affect muscle performance?
- 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
What is the greatest muscle contraction for scar tissue remodeling?
- eccentric contractions
68
How does fatigue relate to force production?
- with increased fatigue there is decreased force production - with increased force production = increased rate of fatigue
69
How does fatigue relate to recruitment of motor units?
- increased fatigue = increased recruitment of larger motor units
70
How does fatigue relate to muscle fiber type?
Type 1: - fatigued by low-intensity, long duration - longer rest time Type 2: - fatigued by high-intensity, short duration - shorter rest time
71
How does fatigue relate to types of muscle activations?
Concentric: - more fatiguing Eccentric: - less fatiguing - leads to DOMS
72
What is DOMS?
Delayed onset muscle soreness - this is a strain related injury to the forcefully stretched muscle during ECC training
73
What happens to a muscle with reduced use?
- atrophy - loss in strength - reduced protein synthesis - increased number of type 1 fibers with immobilization
74
What happens to a muscle if immobilized in a shortened position?
- 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
What happens if a muscle is immobilized in lengthened position?
- increased sarcomere numbers BUT decreased sarcomere length - increased perimysium & endomysium - increased max tension capacity - passive tension is better
76
What can therapists do to mitigate the effects of disuse from immobilization?
- early mobilization as early as possible - if in cast, RIGHT when cast is off move it
77
What is senile sarcopenia?
- decreased number of fibers and size of those fibers (especially type II) - loss in muscle tissue with advanced age
78
What changes occur in muscle tissue because of senile sarcopenia?
- 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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