Tendon & Ligament Biomechanics

Question 1

What are tendons and ligaments made of

Answer 1

• dense, regular connective tissue
• resist tensile forces

Question 2

Function of ligaments

Answer 2

• transmit tensile force from bone to bone
• provide stability
• permit jt motion

Question 3

Ant & post vertebral ligaments

Answer 3

• fibres span may levels (superficial)
• fibres cross only adjacent vert (deep)
• shorter fibres less likely to be damaged

Question 4

Purpose of plantar ligaments

Answer 4

• 2 longitudinal and 1 transverse
• adapt to surfaces and dampen impact forces

Question 5

ACL function

Answer 5

• resist ant tibial translation and rotation
• non-linear load curve
• can stabilise knee in various positions and loading

Question 6

Tendon function

Answer 6

• transmit force from muscle to bone
• absorb store and release energy (conserves energy so muscles don’t have to do all the work)
• power amplification > release energy fast
• protect muscle from damage > shock absorber

Question 7

Factors of energy storage tendons and eg

Answer 7

Achilles and patella tendon
- increased elasticity and fatigue resistance

Question 8

What makes a tendon buffer or amplify

Answer 8

Buffer - tendons lengthen before landing from a jump or walking down a hill to prevent eccentric damage

Amplifier - during stance, slowly stores energy and releases in next mvt

Question 9

Anatomy of achilles for function

Answer 9

• fascicles of tendon spiral
  > allows elongation, elastic recoil
  > LG and soleus insert w strong torsion
• helps with intra-tendinous strain distribution

Question 10

What is an aponeurosis that stores energy

Answer 10

ITB

Question 11

Tendon properties that affect muscle output

Answer 11

• more compliant = requires more contraction before force generated
• electro-mechanical delay > delay between activation and production of force

Question 12

What is enthesis

Answer 12

• tendon/ligament to bone insertion
• aids load transfer between it and bone
  Types
  > fibrous (directly onto bone)
  > fibrocartilganous (4 zones w gradual transition)
  > muscular (muscle straight onto bone no tendon)

Question 13

What is muscle-tendon junction

Answer 13

• no transition
• collagen and muscle interdigitate
  this increases SA and reduces stress on structures

Question 14

What are some structures that surround tendons and what do they do

Answer 14

• fibrous sheaths/retinaculae > stability
• synovial sheaths or fluid > less friction
• bursae > reduces compression

Question 15

Type of collagen in tendons

Answer 15

Type I

Question 16

Proteoglycans in tendons

Answer 16

• distribution varies along tendon (more at insertional part)
  Decorin > transfers load between collagen fibrils
  Lubricin > lubrication of tendon surface

Question 17

Ligament structure

Answer 17

mainly type I, some elastin, varied collagen arrangment

Question 18

Tendon structure

Answer 18

mainly type I
small amt elastin
Decorin
collagen in tensile direction

Question 19

Tendon hierarchical structure

Answer 19

collagen > microfibril > subfibril > fibril > fascicle > tendon

Question 20

Overall behaviours of ligaments and tendons

Answer 20

anisotropic (behaviour depends on direction)
heterogenous
viscoelastic

Question 21

Stress-strain curve of tendon

Answer 21

Physiological region > match between stress/strain, fibres will return to normal after load removed

Overuse injury region > inadequate match, plastic deformation > microtears or adaptation depending on point

Tendon rupture

Question 22

Ligament stress-strain

Answer 22

Lower slop of elastic region
Microfailure in plastic region
Resists more then fails

Question 23

How will a tendon change after repeated loading in overuse region

Answer 23

• energy released
• stiffness decreases
• becomes more compliant
• deforms more

Question 24

How do tendons and ligaments react to heat

Answer 24

increases stress-relaxation and creep

Question 25

What happens to tendons and ligaments w maturation

Answer 25

Maturation > better strength and stiffness Ageing > gradual decrease in mechanical properties

Question 26

Patella tendon difference adults v children

Answer 26

Adults - larger and stiffer Bcoz of increased collagen diameter Increased CSA

Question 27

What is Sever's disease

Answer 27

calcaneal apophysitis - inflamation of growth plate children 8-11 > overuse problem

Question 28

Osgood schlatter disease

Answer 28

tibial tuberosity apophysitis ages 13-14 (boys) and 11-12 (girls)

Question 29

Aging effects on muscle

Answer 29

- decrease muscle mass - fewer number and size of muscle fibres - less capacity to detect info and activate muscles - strength decreases

Question 30

How does the Achilles tendon change w age

Answer 30

- more compliant - less contractile force - less rate of force - less stiff

Question 31

Positive impacts of exercise in older adults

Answer 31

- less muscle loss - neural adaptation - better quality of life - prevents falls

Question 32

Exercise effect on tendons

Answer 32

With high loads, high tendon strains and isometric exercises > more stiffness and hypertrophy endurance - same stiffness stretching - decrease stiffness isometric, concentric, eccentric, plyometric - increases stiffness)

Question 33

Mechanics of ligament injury

Answer 33

- tensile load exceeds capacity - awkward landing - joint dislocation - abnormal motion of bony articulation

Question 34

Grades of ligament injuries

Answer 34

Grade1- damage to some collagen Grade2- more extensive damage Grade3- complete rupture

Question 35

What are the 3 healing phases of ligaments

Answer 35

- inflammation - proliferation - remodelling

Question 36

Phases and times of ligament rupture healing

Answer 36

10 days - injury filled with inflammatory tissue 3 wks - inflammatory subsides and active fibroblasts come in 6 wks - less numbers and size of fibroblasts > more longitudinal alignment of nuclei 14wks - remodelling > better alignment and fewer cells 14-40wks - few changes

Question 37

Mechanical + morphological properties of an injured ligament

Answer 37

- decreased stiffness - decreased load at failure - entire ligament is weakened - larger CSA and increased laxity

Question 38

Extra v Intra articular ligament injuries

Answer 38

Extra > high healing capacity (vascular), treated conservatively Intra> lower healing capacity, require surgery

Question 39

MOI for tendon injuries

Answer 39

1. excessive force 2. repeated overload 3. normal forces applied to weakened tendon 4. stress-shielding 5. forces applied in alternate direction

Question 40

Sites of tendons

Answer 40

Mid substance Insertional Musculotendinous junction

Question 41

What is paratendinitis

Answer 41

Tendon rubs over bony protuberance Inflammatory cells Crepitus

Question 42

Difference between overuse and normal tendon

Answer 42

Overuse - grey and amorphous, disorganise collagen, no immune cells, hypervascularity, more PG and water content Normal tendon - highly organised, few cells, white in appearance

Question 43

Components of tendon rehab

Answer 43

- exercise > reduces pain, better loading capacity, better function, remodels it - no compressive loading

Question 44

What does immobilisation do to tendons/ligaments

Answer 44

decrease in structural properties - weaker, more disorganised collagen - decrease in stiffness - decrease deterioration w tension