Ligamentous injuries of knee Flashcards
Ligaments are
type 1 collagen
designed to resist tension
and provides stability
strength of ligament depends on the size and thickness and what is the age and general health of the individual
Scar develops in the form of type
Type three collagen
not as strong
make up of early healing ligament
less organized Fiber alignment
altered proteoglycan content
fewer Collagen cross-links
increased vascularity
Decreased innervation
weaker
Decreased proprioception
Immobilization and ligament recovery
do not immobilize for more than a week or two
protected movement is important to initiate healing
However, immobilization can be harmful
ligament can start to atrophy - decrease tensile strength
Insertion into the bone recovers…
first, within weeks
While the ligament takes longer, within months
MCL resists
valgus stress
External rotation
in the MCL, which layer is more commonly injured
Superficial layer
MCL deep fibers tend to attach to the
Medial meniscus and medial joint capsule
when are the MCL fibers more taut
Posterior fibers are taut than anterior fibers with the knee extended
Anterior fibers are more taut in slight knee flexion
mechanism of injury of MCL
Valgus trauma
often With planted foot
Local pain, swelling, difficulty walking, instability with activities
valgus stress test
Push knee medially while using your body and elbow to increase valgus stress by creating a counter force
30° flexion first then if positive test in full extension
A positive positive finding is pain reproduction in the area you are testing, as well as increased movement or a lack of a firm end feel
LCL resist
varus stress
ER
LCL is separated from the capsule by
popliteus tendon
LCL is not attached to the meniscus
mechanism of injury of LCL
varus trauma
Often with planted foot
Local pain, swelling, difficulty walking instability with activities
varus stress test
push me laterally while using your body and elbow to increase the varus stress by creating a counter force
Test 30° function first then positive test in full extension
Positive finding is pain reproduction in the area you are testing, as well as increased movement or lack of end feel
unreliable assessment
grading ligament sprains
Grade 1- pain with stress testing no instability
Grade 2 - pain with stress testing positive instability, but with firm end feel
Grade 3 - complete tear, positive instability, no firm end feel, may have less pain due to complete ligament rupture
ACL resists
Anterior translation of the tibia on the femur
Hyper extension of knee
Internal rotation of tibia on femur
Anteromedial bundle of the ACL
maintains tension throughout the knee range of motion, especially 45 to 60° flexion
Posterolateral bundle of ACL
taut in extension
Slack once knee flexes
once the knee flexes to 90°, what happens to ACL
Anteromedial and posterolateral bundles cross over each other
MOI ACL
80% noncontact- cutting pivot on fixed foot, rotational, valgus, hyper extension
20% contact- posterior directed force on distal femur or medial directed force on lateral knee when foot is planted
Significant knee pain, swelling, popping, episodes of knee giving away, quads inhibition, loss of range of motion
Lachmans test
ACL
knee tested at about 20 to 30° flexion
Attempt to glide the tibia anteriorly
Positive test is mushy or soft end feel
anterior drawer test
ACL
Knee in 90° flexion
Slightly abduct externally rotate hip to improve hamstring relaxation
Draw tibia anteriorly
Positive test is greater than 5 mm of movement
Assess position tibia to avoid false positive or negative
lever test
ACL
full knee extension
rest fist under proximal third of the calf
other hand will apply anterior to posterior force on the distal third of the quadriceps
Positive test is no elevation of the heel
PCL resists
Posterior translation of tibia on femur
Rotation of tibia on femur
Provides posteriolateral stability of knee joint
What other structures help provide stability of the posteriolateral corner
lateral head of gastrocnemius
Popliteus
poplitealfibular Ligament
LCL
arcuate ligament
PCL in comparison to the ACL
PCL is 50% thicker and twice the tensile strength compared to the ACL
what are the bundles of the PCL
Anterolateral
Posteromedial
PCL is more taut in
Knee flexion
MOI PCL
high impact posterior directed force on the tibia
MVA with shin to dashboard
acute onset of posterior knee pain , swelling, instability
posterior drawer test
knee in 90 flexion
hold proximal tibia with hands so that thumbs are on anterior joint line and fingers can palpate hamstring tendons
Push tibia posteriorly
positive test is excessive movement of the tibia compared to the other side or a lack of end feel
posterior sag sign
Patient supine with knees flexed 90°
Observe the position of the tibial, tuberosities and plateau
Positive test is posterior displacement of involved tibia
Patient contract hamstrings to see if that further displaces involved tibia posterior
