Ligament & Tendon Flashcards
Tendons & ligaments are what kind of connective tissue?
dense, regular
How do the superficial & deep layers differ in both the anterior & posterior longitudinal ligament?
the superficial layers span multiple spinal levels whereas the deep only cross adjacent vertebra attaching to the annulus fibrosis
Where are the anterior & posterior longitudinal ligaments thickest?
in the thoracic region
Why is the ligamentum flavum so important to posture?
it lines the vertebral canal and is under constant tension which prevents the spine from buckling during movement
How many archs do we have underfoot?
3 (2 longitudinal & 1 transverse)
What determines the arrangement of the archs?
bony arrangement of the foot, plantar ligaments & plantar aponeurosis
What is the purpose of the arch underfoot?
shock absorption
What does the ACL resist?
anterior tibial translation & rotation
What is the function of a tendon?
transmit force from muscle to bone
absorb, store & release energy
power amplification
protect muscle from damage
What are the two predominant energy storing tendons?
patellar & achilles
At what percentage of strain do tendons fail? When does an achilles fail?
3-8%, achilles up to 12%
How much does the achilles tendon contribute to total body work through energy storage and release during a single leg hopping task?
16%
What is buffering of a tendon?
a protective feature whereby the tendon lengthens before a muscle during an eccentric contraction
What is amplification (as performed by the achilles during gait)?
during stance the Achilles tendon slowly stores and quickly releases energy during push-off to propel to the next step
What is electro-mechanical delay? What affect does stiffness/compliance have on this delay?
the delay between the activation of a muscle and its production of force around a joint
a more compliant tendon will have a bigger delay, stiffer will have a smaller delay
this is because it takes more time to take up the slack in a compliant tendon before force around a joint can occur
What is the enthesis? How does it differ from the muscle-tendon junction?
the gradual insertion site of the tendon/ligament to bone which allows load transfer between the elastic tendon/ligament and rigid bone
muscle-tendon junction is the abrupt transition from muscle to tendon whereby collagen fibers and muscle cell membrane interdigitate to increase surface area and reduce stress
Name the cells and 3 main components of ECF present in tendons
Tenocytes, collagen, elastic & proteoglycans
What collagen types are present in tendons?
Type 1 (90%) & type 3 (10%)
Where are there relatively more proteoglycans found within a tendon and why?
towards the insertional regions of tendons because that is where tendons are most subjected to compression and the PG’s attract water to resist this compression
Is collagen arrangement linear or variable in ligaments?
variable
Describe the tendon hierarchical structure
collagen > microfibril > sub-fibril > fibril > fascicle > tendon
Are ligaments & tendons highly vascularised?
No- hence slower to recover than muscles
Mechanical behavior of tendons/ligaments depends on what two factors?
direction and type of forces (i.e. compressive vs tensile)
What is the difference between ‘stiffness’ & Young’s modulus of a ligament/tendon?
stiffness refers to the structural properties of a particular tendon/ligament whereas Young’s modulus refers to the material properties of the actual ligament/tendon material despite its size/shape
How much strain do normal physiological movements put on tendons?
0-3%
At what percentage of strain do most tendon overuse injuries occur?
between 3% & 8%
At what point of strain do tendons typically fail?
8% (Achilles is the exception at 12%)
What are some key differences between tendons & ligaments?
tendons have a much smaller toe region, stiffer linear region
but mainly:
tendons fail abruptly while ligaments fail progressively
this is due to the alignment of the collagen fibrils which are varied in ligaments & linear in tendons
What is creep?
when a tissue is constantly loaded the length of that tissue will gradually increase with time (so it has a non-linear recovery)
How might creep impact upon joint stability
creep within ligaments due to a sustained posture (i.e. bending over) will cause slack in the ligaments and therefore a decrease in stability
What is stress-relaxation?
if tissue is stretched to a fixed length, over time the force will dissipate
What is hysteresis?
as a tissue is loaded & unloaded, some energy is lost as heat
What kind of injury is more likely from a tendon under a low-loading rate?
avulsion fracture
What kind of injury is more likely from a tendon under a high-loading rate?
mid-substance tear
What effect does heat have on the stress-relaxation of tendons/ligaments
it will increase the stress-relaxation (at over 40 degrees)
Why are adolescents more prone to tendon-bone insertional problems compared to adults?
there is an asynchronous maturation of mid-substance and bone-tendon junction so prior to skeletal maturity, tendons are stronger mid-substance than at the bone-tendon junction which makes avulsion fracture more likely than a mid-substance injury
What is Sever’s disease?
calcaneal apophysitis (irritation of the growth plate at the heel) affecting children 8-11 years, seen in kids with a sudden increase in activity
What is Osgood Schlatter disease?
tibial tuberosity apophysitis affecting children 11-14 years, seen in children who play alot of sport
True or false… tendons are just as good at self-renewal as muscles
false
Do achilles become more or less stiff with age?
less- more compliant
Do muscles become more or less stiff as we age?
more stiff
What factors need to be considered when attempting to increase the stiffness of a tendon with exercise?
type/direction of loading (isometric at length, concentric, eccentric & plyometric)
magnitude of loading (needs to induce 3-5% strain in order to see alternations in stiffness without injury)
length of exercise intervention (at least 8 weeks, 14 weeks ideal)
What are the 3 grades of ligament injury?
Grade 1: damage to some collagen fibres
Grade 2: extensive number of fibres damaged
Grade 3: complete rupture
What are the 3 overlapping healing phases of a ligament?
- Inflammation
- Proliferation
- Remodelling
What mechanical defects are seen in healed ligaments?
decreased stiffness, decreased load at failure, failure often seen at midsubstance (as the entire ligament is now weakened)
Does the cross section of a ligament increase or decrease during/after healing? What affect does healing have on the laxity?
laxity increases despite the CSA increasing
How does the different healing capacity of intra-articular & extra-articular ligament injuries influence the treatment choice?
extra-articular have a higher healing capacity and are often treated conservatively, intra-articular have a lower healing capacity and are often treated surgically
What other injuries are ligament injuries often associated with?
bone bruising, OA & instability
What are the 5 mechanisms of tendon injury?
- excessive force
- repeated overload
- normal forces applied to a weakened tendon (i.e. after a period of immobilisation or detraining)
- stress-shielding (where some fibres and overloaded while others are underloaded)
- force applied at unusual direction
What is paratendinitis?
Damage to the tendon sheath from where a tendon rubs over a bony protuberance (i.e. flexor hallicus longus over medial maleolus)
What is occuring on a cellular level during an overuse tendinopathy?
increased cellularity
hypervascularity
increased proteoglycans & water content
disorganised collagen
How does a patellar tendinopathic tendon differ mechanically from a healthy tendon? How about an achilles tendinopathic tendon?
patellar tendon gets stiffer while an achilles tendon gets more compliant
Why should we immobilise injured tendons/ligaments? What positioning is important with immobilising?
allow the inital healing to commence but it must be done under tension to minimise negative affects of immobilisation (decreased stiffness and decreased load to failure)
Are midsubstance or insertional injuries slower to recover?
insertional
How does the anatomy at musculotendinous junctions provide protection against injury?
the interdigitation of collagen fibres and muscle cell membrane increase the surface area of the junction allowing load to be distributed better and reduce stress
How does the arrangement of collagen fibres within ligaments & tendons differ? How does this relate to the shape of its load-deformation curve?
tendon: uniaxial arrangement, results in an abrupt failure
ligament: multiaxial arrangement, results in a progressive failure
Describe the changes in ligament cross-sectional area post-rupture
collagen alignment is altered, vascularity increases & more cells are present
What types of loads are most likely to cause mid-substance tendinopathy vs insertional tendinopathy?
insertional: compressive loads
mid-substance: tensile loads
