Co#ective Ti+ue
Biochemical Structure of Tendons
TENDON INJURIES AND PROPERTIES
Types of musculoskeletal connective tissue
• Tendons – connects muscle to bone
• Ligaments – connect bone to bone
o Tendons and ligaments have very similar properties and structure, but different functions
• Bones
• Cartilage
• Epimysium, perimysium and endomysium in skeletal muscle
Intramuscular connective tissue
• White layer surrounding each cell = endomysium
• Cannot see the epimysium
• Under scanning electron microscope, cells removed > connective tissue remaining
Why is connective tissue important?
• Increased risk of non-communicable disease in sedentary individuals
• Use physical activity in the prevention of disease, maintenance of health and treatment =
rehabilitation
• Sporting excellence and injury prevention for elite and recreational athletes
Musculoskeletal injuries
• Musculoskeletal tissue = bones, tendons, ligaments, muscles
• Commonly injured as a result of PA and work-related activities (repetitive movements)
(1) Acute onset injuries – result of a single macro-traumatic event, resulting in tissue injury
o Tissue is acutely overloaded and fails
(2) Chronic injuries (overuse) – tissue eventually becomes painful when subjected to multiple
repetitive stresses that it is not able to withstand
o Initially unaware of tissue damage
o Microscopic damage – important for adaptation but if not treated properly it can grow in
volume and become symptomatic e.g. pain
o Accumulation of micro-traumatic events
Tendons
• Connect muscle to bone
• Transmit force emanating from muscle to bone to generate movement
• Other functions:
o Store elastic energy – stored energy propels individual for subsequent movement
o Serve as an articulating surface
o Can form part of the pulley system
• Muscle contraction = shortening ® tendon stretched, storing potential energy
,• Shows resistance to mechanical loads e.g. Achilles tendon has to withstand 10x our body weight
Tendon has two specific structures:
• Myotendinous junction (MTJ) – the point of union with muscle
o Sarcolemma of muscle is folded, increase SA for tendon to join the muscle
o Subjected to great mechanical stress during transmission of muscular contractile force to
the tendon
• Osteotendinous junction (OTJ) – the point of union with bone
o tendon to cartilage to bone
o enthesis – the insertion of a tendon, ligament, capsule or fascia into bone
• Most musculoskeletal tissue conditions are multi-factorial – there is not a single cause
• Many factors increase the risk for injuries
• Often do not understand these causes, rather address risk factors
• Intrinsic factors – biomechanics, sex, flexibility, anatomical variations, genetics, age,
anthropometry, previous injury
• Extrinsic factors – medications, nutrition, environmental conditions, equipment, physical activity,
training errors
Pathogenesis – risk and management
Determining the risk, diagnosis, clinical management and therapeutic interventions should be based on
a solid understanding of underlying biological mechanisms that cause injury
• Limited knowledge of the biological mechanisms, more research required
• Affect ability to accurately diagnose + clinical management
Chronic tendinopathy
• Collagen (protein fibre – main proteins found in tendons
o Arranged in highly ordered structure parallel to one another
• (a) normal flexor tendon histology
• (c) accumulation of GAG (blue) surrounded rounded cells in the
matrix
o Ground substance
o Formation of new blood vessels that should not be there
o Irreversible
NOTE: REFER TO ‘STRUCUTURE AND METABOLISM OF TENDONS’, O’BRIEN
, Viscous, elastic, and viscoelastic properties
Viscous material • E.g. honey
• Does not stretch when a force is applied to the material
• Flows like liquid
• Material does not return to its original shape when the force is
removed
• Friction due to sliding
Elastic material • Stretched when a force is applied to the material
• Returns to its original length when the force is removed
• Energy storage and return
Viscoelastic material • Elastic and viscous components
• When force is applied:
o Spring properties stretches first
o Viscous properties will then start to flow
o Spring will gradually return to its original shape
• History dependent mechanics – what happens when the force is
removed depends on its current and prior load
• Tendons and ligaments are highly viscoelastic
Features of Viscoelastic behaviour
1. Hysteresis – the dependence of a state of a system on its history
• Loading (up) and unloading (down) curves are different
• Something getting longer with an increasing loading
o As you pull (increase load), approached maximum elongation
• Grey region = energy lost
o When release, tendon goes back to normal but not through
the same load
o Less energy can be used to return the material back to normal
• As one loads and unloads a tendon, some energy is lost as heat
• Greater hysteresis = greater energy lost as heat = less energy can be recoiled to propel
movement
2. Rate dependence
• Material behaves differently depending on the load you apply to the tissue
Biochemical Structure of Tendons
TENDON INJURIES AND PROPERTIES
Types of musculoskeletal connective tissue
• Tendons – connects muscle to bone
• Ligaments – connect bone to bone
o Tendons and ligaments have very similar properties and structure, but different functions
• Bones
• Cartilage
• Epimysium, perimysium and endomysium in skeletal muscle
Intramuscular connective tissue
• White layer surrounding each cell = endomysium
• Cannot see the epimysium
• Under scanning electron microscope, cells removed > connective tissue remaining
Why is connective tissue important?
• Increased risk of non-communicable disease in sedentary individuals
• Use physical activity in the prevention of disease, maintenance of health and treatment =
rehabilitation
• Sporting excellence and injury prevention for elite and recreational athletes
Musculoskeletal injuries
• Musculoskeletal tissue = bones, tendons, ligaments, muscles
• Commonly injured as a result of PA and work-related activities (repetitive movements)
(1) Acute onset injuries – result of a single macro-traumatic event, resulting in tissue injury
o Tissue is acutely overloaded and fails
(2) Chronic injuries (overuse) – tissue eventually becomes painful when subjected to multiple
repetitive stresses that it is not able to withstand
o Initially unaware of tissue damage
o Microscopic damage – important for adaptation but if not treated properly it can grow in
volume and become symptomatic e.g. pain
o Accumulation of micro-traumatic events
Tendons
• Connect muscle to bone
• Transmit force emanating from muscle to bone to generate movement
• Other functions:
o Store elastic energy – stored energy propels individual for subsequent movement
o Serve as an articulating surface
o Can form part of the pulley system
• Muscle contraction = shortening ® tendon stretched, storing potential energy
,• Shows resistance to mechanical loads e.g. Achilles tendon has to withstand 10x our body weight
Tendon has two specific structures:
• Myotendinous junction (MTJ) – the point of union with muscle
o Sarcolemma of muscle is folded, increase SA for tendon to join the muscle
o Subjected to great mechanical stress during transmission of muscular contractile force to
the tendon
• Osteotendinous junction (OTJ) – the point of union with bone
o tendon to cartilage to bone
o enthesis – the insertion of a tendon, ligament, capsule or fascia into bone
• Most musculoskeletal tissue conditions are multi-factorial – there is not a single cause
• Many factors increase the risk for injuries
• Often do not understand these causes, rather address risk factors
• Intrinsic factors – biomechanics, sex, flexibility, anatomical variations, genetics, age,
anthropometry, previous injury
• Extrinsic factors – medications, nutrition, environmental conditions, equipment, physical activity,
training errors
Pathogenesis – risk and management
Determining the risk, diagnosis, clinical management and therapeutic interventions should be based on
a solid understanding of underlying biological mechanisms that cause injury
• Limited knowledge of the biological mechanisms, more research required
• Affect ability to accurately diagnose + clinical management
Chronic tendinopathy
• Collagen (protein fibre – main proteins found in tendons
o Arranged in highly ordered structure parallel to one another
• (a) normal flexor tendon histology
• (c) accumulation of GAG (blue) surrounded rounded cells in the
matrix
o Ground substance
o Formation of new blood vessels that should not be there
o Irreversible
NOTE: REFER TO ‘STRUCUTURE AND METABOLISM OF TENDONS’, O’BRIEN
, Viscous, elastic, and viscoelastic properties
Viscous material • E.g. honey
• Does not stretch when a force is applied to the material
• Flows like liquid
• Material does not return to its original shape when the force is
removed
• Friction due to sliding
Elastic material • Stretched when a force is applied to the material
• Returns to its original length when the force is removed
• Energy storage and return
Viscoelastic material • Elastic and viscous components
• When force is applied:
o Spring properties stretches first
o Viscous properties will then start to flow
o Spring will gradually return to its original shape
• History dependent mechanics – what happens when the force is
removed depends on its current and prior load
• Tendons and ligaments are highly viscoelastic
Features of Viscoelastic behaviour
1. Hysteresis – the dependence of a state of a system on its history
• Loading (up) and unloading (down) curves are different
• Something getting longer with an increasing loading
o As you pull (increase load), approached maximum elongation
• Grey region = energy lost
o When release, tendon goes back to normal but not through
the same load
o Less energy can be used to return the material back to normal
• As one loads and unloads a tendon, some energy is lost as heat
• Greater hysteresis = greater energy lost as heat = less energy can be recoiled to propel
movement
2. Rate dependence
• Material behaves differently depending on the load you apply to the tissue
