lec 6 - ligament and joint injury Flashcards
what is the structure of ligaments
dense bands of collagen tissue (less uniform than tendons)
- vary in size, shape, orientation, and location
what is the function of ligaments
- connect bone to bone
- passive stabilisation of joints (don’t have to activate)
- important proprioceptive function
what is the response to ligament injury
- decreased proprioception (nerve endings damaged)
- leads to reinjury
- ligament scars can creep (increased laxity)
what does joint stabilisation depend on
passive, active, and neural subsystems
what is the passive subsystem
non contractile connective tissues passively stabilising joint
- ex. bones, ligaments, cartilage, etc
what is the active subsystem
controlled by the neural subsystem to provide dynamic joint stability (protects joints from injuries)
- ex. muscles and tendons
what happens if load exceeds the active subsystems capacity
load gets transferred over into the passive subsystem
- when bone/ligament injuries occur
what is the difference between intra articular, extra articular, and capsular ligaments
intra articular - within the joint (ACL, PCL)
extra articular - additional support for the joint (MCL, LCL)
capsular - thickenings of the joint capsule (ankle ATFL)
what is the difference in blood supply in 3 types of ligaments
capsular = best blood supply
intra articular = worst blood supply
what is the ligaments adaptation to training
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%
on a stress strain curve, when will collagen fibres in the ligament start to rupture
when the force causes more than a 4% change in length
what category of injury is most likely to occur in ligaments
acute sudden event injuries (identifiable event - joint in extreme position)
can repetitive injuries occur in ligaments
yes - can occur as the ligaments gradually stretched out
- ex. UCL creep in pitchers leading to injury
what determines a grade 1 ligament injury
mild, structural damage on the microscopic level
- no instability
what determines a grade 2 ligament injury
moderate, partial tear, swelling and pain
- no / limited instabilty (laxity to varying degrees)
very large range - highly variable
what determines a grade 3 ligament injury
severe, full rupture, significant swelling
- instable
what is hemoarthrosis
bleeding into the joint
- caused by ACL tear (70%), peripheral meniscus tear, osteochondral injuries or fractures
what are the 2 bundles of the ACL and their functions
anteromedial bundle - resists tibial anterior translation (relaxed in extension, tight in flexion)
posterolateral bundle - resists tibial rotation (tight in extension, relaxed in flexion)
what are the three physical exams you can do for an ACL injury
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
what is the unhappy triad of knee injuries
ACL, MCL, meniscus
what are possible complications of ACL injury
osteochondral injury
osteoarthritis in 15-20 years (long term conseqeunces)
what is the bucket handle meniscus tear
part of meniscus tears and flips over on itself and can’t come bakc
- leads to locked knee in flexion (needs surgery)
when is an ACL graft weakest and when is reinjury most common
weakest = 3-6 months
highest reinjury = 2 years
where do ACL grafts come from and why
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)
