Term
| what are some similarities between tendons and ligaments? |
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Definition
PASSIVEbut contributes to joint motion.
Dense CT
Not well vascularized |
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Term
| what are the mechanical roles and sensory roles of ligaments and joint capsules? |
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Definition
Mechanical Role
–Joint stability (bone to bone)
–Prevents excessive motion
–Guides joint motion
• Sensory Role
–Provides feedback to CNS |
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Term
| what is the function of tendon? |
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Definition
Transmits tensile loads
from muscle to bone
• Makes muscle more
efficient
–Provides optimal muscle
belly location
• Sensory Role |
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Term
| what is the structure of tendon? |
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Definition
| fibroblasts (tenocytes) type I collagen, elastic fibers |
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Term
| what is the structure of ligament? |
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Definition
Intra-articular and extra-articular ligaments
fibroblasts
type I collagen. elastic fibers. |
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Term
| what are the differences in composition of tendons and ligaments? |
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Definition
tendons are 20% cellular, 80% ECM
ligaments are 70% water, 30% solids (collagen ground substance elastin) |
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Term
| endontenon, epitenon, paratenon. what is paratenon? |
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Definition
PARATENON
– fatty areolar tissue to assist gliding
- can be a tendon sheath (synovial)
Surrounds the tendon
where it passes under or
around bones and bands
of connective tissue
- Secretes a thin layer of
synovial fluid aids
lubrication |
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Term
| what are the 4 zones of insertion into bone? |
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Definition
4 zones of insertion into bone
zone 1 parallel collagen fibers
zone 2 unmineralized fibrocartilage
zone 3 mineralized fibrocartilage
zone 4 cortical bone |
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Term
| what are direct vs indirect insertions of ligaments? |
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Definition
DIRECT - Ligament
• Uncalcified fibrocartilage
• Mineralized fibrocartilage
• bone
INDIRECT - superficial layer connects to
periosteum
• deep layer connects to
bone via Sharpey’s fibres |
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Term
| how is the tendon supplies with blood? |
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Definition
Musculo‐tendinous 1/3
vessels from perimysium
Middle 1/3
vessels mainly emanate from the
epitenon where longitudinal vessels
run into the endotenon
Tendon‐bone 1/3‐
vessels from periosteal insertion
Vascular portion
– surrounded by a paratenon, not
synovial sheath
– vessels enter the tendon from
many points and connect with a
longitudinal system of
capillaries
• Avascular portion
– surrounded by synovial
sheath
– Other pathways for
nutrition? synovial pathway
“diffusional nutrition” |
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Term
| how is ligament supplies with blood? |
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Definition
HYPOVASCULAR
–uniform vascularity supplied through arterial plexuses
surrounding the joint
• Intra‐articular ligament’s blood supply is LIMITED
–diffusion necessary
–Differentiate from knee extra‐capsular/intraarticular |
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Term
| what are the sensory roles to tendons and ligaments? |
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Definition
Afferent commands to…
–Spinal cord
–Brainstem/cerebellum
–Cortex
• Process and send efferent commands to
muscle |
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Term
| what are the sensory organs of tendons? |
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Definition
Golgi Tendon Organs
–Tension or rate of tension development |
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Term
| what are the sensory organs of ligaments? |
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Definition
Ruffini endings
–Joint position (intra‐articular
pressure, magnitude and
velocity of movement)
• Pacinian corpuscles
–pressure
• Golgi tendon organ‐like
–Tension
• Free nerve endings
–Pain from mechanical or
chemical origin |
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Term
| where does the strength of tendons and ligaments come from? |
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Definition
Predominantly Type I ‐ orderly parallel arrangement
• Synthesized by fibroblasts
–arranged in long parallel rows in spaces between collagen bundles
– relatively inactive cells
• Strength related to number and size of collagen fibrils
–Crosslinking
–Reduces with age |
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Term
| what is the ground substance of tendons and ligaments? |
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Definition
Proteoglycans
–Glycosaminoglycans bound to HA
–Similar to articular cartilage
• Provides lubrication and spacing to aid in the
sliding of fiber – viscoelastic behaviors |
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Term
| what are the biomechanical behaviors of tendons and ligaments? |
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Definition
Viscoelastic (fluid and solid component)
• Strength –Has one of the highest tensile strengths
of any soft tissue
–High % of collagen
–Collagen orientation (anisotropy)
–Tensile strength related to # and quality of
collagen crosslinks
• Flexibility
–Elongation due to interfibrillar sliding and shear of
ground substance |
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Term
| what is the strain rate dependence of tendon and ligament? |
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Definition
HIGH strain rate
–stiffer & stronger
–more energy stored
• greater force required
to rupture
• LOW strain rate
–Failure at lower stress |
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Term
| What are the properties of the bone-ligament-bone complex? |
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Definition
Low strain rate
–Bony insertion of the ligament was the weakest
link
• High strain rate (typical injury mechanism)
–Ligament was the weakest link
• How? |
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Term
| how does repetitive loading affect T and L's? |
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Definition
Curve shifts to the right
–Less stiff
–Plastic deformation |
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Term
| how does age effect tendon? |
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Definition
Maturation with Development
# and quality of collagen cross‐links increases
Increased collagen fibril diameter
cross‐sectional area of tendon increases
Aging
Collagen content decreases
↓ collagen turnover rate
decrease individual fibril CSA, but increase fibril number
tissue becomes stiffer, but remains strong
less deformation at a given load
Differentiate from immobility (although difficult in reality) |
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Term
| what are some hormonal or drug interactions with T and L's? |
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Definition
Pregnancy
–Increased laxity
–Decreased stiffness
• Diabetes
–Stiffer (less elastic)
–Tendon contractures
Pharmacology
–NSAIDs
• tensile strength
–Increased collagen
proportion
–Increased collagen cross‐
linking
–Corticosteroids
• ↓ strength with injections
–inhibitory effects on GAG
synthesis, proteins,
collagen |
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Term
| how does immobilization affect T and L's? |
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Definition
Weaker/less stiff
• ↑ tissue metabolism
– ↑ immature collagen
– ↓ amount and quality of
collagen cross‐links
• bone resorption at
insertion site
• increased randomness of cells,
fibers, matrix organization
33% of normal with
9 weeks immob |
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Term
| how does MOBILIZATION affect T and L? |
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Definition
Stronger/stiffer
• thicker collagen fibrils
• Muscles/bone will
adapt much faster than
tendon/ligament |
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Term
| what are some tendon injury mechanisms? |
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Definition
Increased stress with increased muscle
contraction
• Cross sectional area
–Muscle ‐↑stress with ↑PCSA
–Tendon ‐↑stress tolerated with ↑CSA
• Failure occurs at the weakest point
–Muscle‐tendon‐bone complex |
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Term
| what is a mid substance tendon rupture? |
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Definition
Pre‐existing pathology or a failure of
normal tendon remodeling prior to
rupture
(eg: Achilles tendon)
2. tendon rubbing against a bony
prominence
(eg: supraspinatus on acromion) |
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Term
| what is a tendon avulsion fracture? |
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Definition
Because tendons can withstand larger
tensile forces than muscle or bone…
= AVULSION FRACTURES
oruptures at the MUSCULOTENDINOUS
junction are more common than MID‐
SUBSTANCE tendon ruptures |
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Term
| How does tendon healing work? |
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Definition
1st week - initial inflammatory response; influx of platelets, neutrophils,
and macrophages; deposition of fibrin
•proliferating tissue from the paratenon invades the gap (wound)
and fills it with undifferentiated and disorganized fibroblasts
•fibroblasts synthesize
collagen Type III - weaker
2
nd
week:
•tendon stumps appear to be fused by a fibrous bridge-can be
present for up to 8 weeks post injury
•collagen fibers oriented perpendicular to long axis
•lots of fibroblast proliferation and collagen production
3-4 weeks:
•collagen fibers oriented parallel to long axis
•secondary remodeling begins replacement of Type III collagen
with type I collagen
•tendon callus
formed
8-12 weeks:3 fold increase in tensile strength
6 months:
minimal differences histologically
between the injured area and normal tendon
repaired region still continues to have
inferior material properties for a year or more
****re-injury!! |
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Term
| what is tendonitis? (mostly acute) |
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Definition
Time frame: Days to 2 weeks
• Time to recovery: 4-6 weeks
• Inflammatory cells/infiltrate |
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Term
| what is tendonosis? (mostly chronic) |
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Definition
Time frame: 6-10 weeks
• Time to recovery: 3-6 months
• Very few inflammatory cells |
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Term
| what are the grades of ligament injury? |
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Definition
Grade I over stretching without disruption of the tissue;
histologically will see small hemorrhages and
tearing
Grade II gross tears and hemorrhaging, strength greatly
reduced
Grade III complete disruption of the ligament |
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