Week 2 Flashcards
• Discuss the indications for imaging in traumatic knee injury (Ottawa Knee Rules)
- Age 55 or over
- Isolated tenderness of the patella (no bone tenderness of the knee other than the patella)
- Tenderness at the head of fibula
- Inability to flex knee to 90 degrees
- Inability to weight bear immediately and in the casualty department (4 steps= unable to transfer weight twice onto each lower limb regardless of limping)
• Describe the common mechanisms of injury of the menisci and ligaments of the knee
Two main sub-groups
Non-contact (80%)
- Valgus stress with knee in ext rotation AND near EROM extension
- Deceleration with an attempt to change direction
- Forced hyperextension
Contact
-Mechanisms = valgus force to knee
Discuss the risk factors for ACL injury
There are 4 subheadings
Biomechanical:
Knee valgus
Anterior tibial shear
Tibial IR or ER
Lateral trunk motion
Dynamic foot pronation
GRF
Neuromuscular:
Relative hamstring recruitment
Hip abduction strength
Limb and trunk proprioception
Gender:
Female 2X8 more at risk
Anatomical: High BMI Femoral notch width Generalised or specific joint laxity Prior injury
• Discuss methods of prevention of non-contact ACL injuries
- Stance foot kept closer to the body’s midline
- Torso kept upright and rotated toward the desired direction of travel
- Increased knee flexion angles
- Control of lateral sway
-Hip neuromuscular control
(isometric hip abduction & ER independantly predict future ACL injury)
Outcomes post ACL Injury
Likely profile of an individual who will return to preinjury level of performance
- Low knee effusion
- Less episodes of knee instability(self reported)
- High IKDC scores(self reported knee function)
Low pain
low TSK 11 score
Higher quadriceps peak torque
Less pre/post surgical change in Tegner score(self reported physical activity)
- = biggest indicator
ACL injury has 3x greater risk of OA after AC treated with recon than contralateral healthy knee
Mechanisms of ACL injury
and the structures affected in order of damage
3-4 kinds
Hyperextension
1 posterior capule torn/stretched
2.ACL
3.PCL
O’donoghues /unhappy triad/Valgus knee force with knee in slight flexion
- Classic presentation:
1. Superficial MCL then Deep MCL
2. Tear of medial meniscus- via pull of MCL on attachment to medial meniscus
3. Rupture of ACL - can also result in # of lateral tibial condyle
- Alternative veiw
1. Superficial MCL then deep MCL
2. Tear of lateral meniscus - compression shearing as lat compartment dislocates posteriorly
3. Rupture of ACL
VARUS FORCE TO THE KNEE- uncommon contact MOI
- Lateral collateral ligament
- ACL tear
- Tear of fibres to popliteus
- Fracture of medial tibial condyle
- Lateral meniscus tear
ACL diagnosis
Patient heard crack/pop.snap Felt knee go in and out Initial intense pain Rapid hot effusion within 2 hours Hemoarthrosis = 80% chance of ACL tear
PE -Exclude PCL & #'s -lachman’s, anterior draw, pivot shift -X-ray for associated bony injury (tibial spine avulsion, postero-lateral tibial plateau injury)
PCL diagnosis
- Posterior sag test
- Stability tests (posterior draw, reverse Lachman’s)
MCL diagnosis
Tender on palpation
Lack of knee extension
Nil or minimal swelling
Positive to valgus testing
(pain, gapping, altereded end feel)
Pain & stiffness with extension & twisting
LCL diagnosis
Nil-minimal swelling Lateral joint line tender on palpation loss of terminal extension Positive varus stress test (pain, gapping, altered end feel)
PCL mechanisms of injury
Falling on tibia/blow to tibia forcing it backwards
Football tackle
Dashboard injury
Forced knee hyperextension injury with foot plantarflexed
Hyperextension ( as complication of ACL rupture)
Role of superficial MCL
Superficial MCL
-Primary restraint to VALGUS loads in all degrees of knee flexion
- primary restraint to ER of tibia
- secondary restraint to Anterior tibial translation
Mechanism of injury of superficial MCL
Valgus force with knee slighly flexed(odonoghues triad)
(MCL only)
Valgus force with knee extended
(Posterio medial capsule also torn)
if more severe ACL may also be affected
Role of LCL
& mechanism of injury
- primary restraint to Varus forces at knee
- Restraint to IR of tibia
Very uncommon
Varus stress to the knee( direct blow to anteromedial tibia)
Kinematics of the menisci of the knee
- With knee flexion the menisci elongate posteriorly
- lateral moves more than medial
- Medial more vulnerable to injury
