lec 6 - ligament and joint injury

Question 1

what is the structure of ligaments

Answer 1

dense bands of collagen tissue (less uniform than tendons)
- vary in size, shape, orientation, and location

Question 2

what is the function of ligaments

Answer 2

• connect bone to bone
• passive stabilisation of joints (don’t have to activate)
• important proprioceptive function

Question 3

what is the response to ligament injury

Answer 3

• decreased proprioception (nerve endings damaged)
• leads to reinjury
• ligament scars can creep (increased laxity)

Question 4

what does joint stabilisation depend on

Answer 4

passive, active, and neural subsystems

Question 5

what is the passive subsystem

Answer 5

non contractile connective tissues passively stabilising joint
- ex. bones, ligaments, cartilage, etc

Question 6

what is the active subsystem

Answer 6

controlled by the neural subsystem to provide dynamic joint stability (protects joints from injuries)
- ex. muscles and tendons

Question 7

what happens if load exceeds the active subsystems capacity

Answer 7

load gets transferred over into the passive subsystem
- when bone/ligament injuries occur

Question 8

what is the difference between intra articular, extra articular, and capsular ligaments

Answer 8

intra articular - within the joint (ACL, PCL)
extra articular - additional support for the joint (MCL, LCL)
capsular - thickenings of the joint capsule (ankle ATFL)

Question 9

what is the difference in blood supply in 3 types of ligaments

Answer 9

capsular = best blood supply
intra articular = worst blood supply

Question 10

what is the ligaments adaptation to training

Answer 10

adapt slowly to increased loading but weaken very rapidly as a result of immobilisation
- loading = increased CSA = stronger ligament
- normal everyday training = maintain mech properties
- systematic training can increase ligament strength by 10-20%

Question 11

on a stress strain curve, when will collagen fibres in the ligament start to rupture

Answer 11

when the force causes more than a 4% change in length

Question 12

what category of injury is most likely to occur in ligaments

Answer 12

acute sudden event injuries (identifiable event - joint in extreme position)

Question 13

can repetitive injuries occur in ligaments

Answer 13

yes - can occur as the ligaments gradually stretched out
- ex. UCL creep in pitchers leading to injury

Question 14

what determines a grade 1 ligament injury

Answer 14

mild, structural damage on the microscopic level
- no instability

Question 15

what determines a grade 2 ligament injury

Answer 15

moderate, partial tear, swelling and pain
- no / limited instabilty (laxity to varying degrees)
very large range - highly variable

Question 16

what determines a grade 3 ligament injury

Answer 16

severe, full rupture, significant swelling
- instable

Question 17

what is hemoarthrosis

Answer 17

bleeding into the joint
- caused by ACL tear (70%), peripheral meniscus tear, osteochondral injuries or fractures

Question 18

what are the 2 bundles of the ACL and their functions

Answer 18

anteromedial bundle - resists tibial anterior translation (relaxed in extension, tight in flexion)
posterolateral bundle - resists tibial rotation (tight in extension, relaxed in flexion)

Question 19

what are the three physical exams you can do for an ACL injury

Answer 19

anterior drawer test - bent at 90deg, pull anteriorly on the tibia
lachman test - bent at 20-30deg, externally rotated, pull anteriorly on the tibia
pivot shift test - tests rotational stability of the ACL

Question 20

what is the unhappy triad of knee injuries

Answer 20

ACL, MCL, meniscus

Question 21

what are possible complications of ACL injury

Answer 21

osteochondral injury
osteoarthritis in 15-20 years (long term conseqeunces)

Question 22

what is the bucket handle meniscus tear

Answer 22

part of meniscus tears and flips over on itself and can’t come bakc
- leads to locked knee in flexion (needs surgery)

Question 23

when is an ACL graft weakest and when is reinjury most common

Answer 23

weakest = 3-6 months
highest reinjury = 2 years

Question 24

where do ACL grafts come from and why

Answer 24

hamstring graft
- common in calgary to preserve patellar tendon for downhill skiing
patellar tendon
- common in soccer players because you want to preserve the hamstring tendon in sprinting sports (hamstring tears are common)

Question 25

why don’t prevention programs work in the real world

Answer 25

• poor athlete and coach buy in
• need training programs implemented
  (ACL injuries are still on the rise - injury rates for girls haven’t changed in 20 years - 6x greater than boys)

Question 26

what are the modifiable risk factors for an ACL injury

Answer 26

training program
- weak hip abductors and external rotators
- increased knee abduction moments during cutting and landing

Question 27

explain the glenohumeral joint

Answer 27

one of the most mobile joints in the body
- passive stabilisation provided by coracoacromial and coracohumeral ligaments
- active stabilisation from rotator cuff and biceps

Question 28

what is dislocation

Answer 28

complete separation fo articulating bones

Question 29

what is subluxation

Answer 29

partial dislocation of articulating bones

Question 30

what is the common mechanism for shoulder dislocation

Answer 30

direct blow to the posterior of the shoulder
landing on outstretched arm (anterior and fracture dislocation)

Question 31

what is the risk of shoulder dislocation recurrence

Answer 31

50-90% depending on the type of sport and shoulder dominance