Knee Flashcards
Femur - mechanical axis
connects hip joint to knee joint
3 degrees from vertical
Femur - anatomical axis
along shaft of femur
6 degrees from vertical
Femur - trabecular system
weak zone at neck
Medial femoral condyle
Thinner
Longer
Lateral femoral condyle
sticks out more - more in line with femoral shaft
Femoral shaft obliquity
femur tilts towards lateral side
Patella surface
longer on lateral side
Tibia - condyles
medial is 50% larger and 3x thicker
Tibial condyles - concave/convex
Convexity is greater posteriorly so the joint is more congruent in extension
Transverse ligament
holds menisci from getting farther apart
Coronary ligament
connection btw menisci and rim of tibia
Medial meniscus attached to what
MCL and semimembranosus
More C shaped
Lateral meniscus attached to what
PCL and popliteal
More O shaped
Bowstring effect draws patella what direction
laterally
Genu valgum
knock knees abnormal angulation of tibia away from midline mechanical axis is displaced laterally medial structures = tensile lateral structures = compressive
Genu varum
bow legged
mechanical axis displaced medially
medial = compression
lateral = tensile
Genu recurvatum
mechanical axis displaced anteriorly
Ant = compression
Post = tensile
Excessive strain on ACL
Q angle
line between patellar tendon and patellar tendon tubercle
usually 14 degrees
Flexion - synovial flow
posteriorly
Extension - synovial flow
anteriorly
LCL
Resists what
Tight and slack in what
Resists varus stress and tibial ER
tight in ext, slack in flex
first resistance to force from medial side
MCL
Resists valgus stress, ER, and ant translation of tibis
Connects capsule and medial meniscus
tight in ext, slack in flex
ACL
resists ant tibial translation and tibial IR
PCL
resists post tibial translation and tibial IR
protects knee with flex
Arcuate popliteal ligeamnt
Reinforces posterolateral capsule
resists varus stress
Oblique popliteal ligament
reinforces posteromed capsule
resists valgua stress
limits ER
resists hyperextension
Parapatellar ligament (retinaculums)
helps hold patella in groove
Flexion
130
Extension
0?
IR
30
ER
40
Open chain arthrokinematics
Tibia on femur
concave on convex = SAME
Close chain arthrokinematics
Femur on tibia
convex on concave = OPP
screw home mechanism
flexion = tibia IR
extension = fbular ER
Most of rotation occurs over last 30 degrees of extension
Close packed
ext
Loose packed
flex 25 degrees
Lateral tibial torsion
knee is forward but foot goes out in lateral direction
Miserable mal alignment syndrome
femoral anteversion throws you into IR
Will have genu valgum, VMO weak, lateral tibial torsion, forefoot pronation
Camel sige
patellar tendon torn - secondary to patella alta
Squinting patella
Patella comes out too far medially
look for flat feet
Classification for articular cartilage damage
stage 1 - softening
stage 2 - fibrillation
stage 3 - deeper fissuring
stage 4 - exposed bone
Gout
elevated serum uric acid and deposition of urate crystals in joint soft tissues and kidneys
Pseudogout
deposit of calcium pyroophosphate crystals
Gout - epidemiology
Males more than females
most common over age 40
Hemophillic arthritis
Medical emergency!!!
blood in joint leads to cartialge degeneration
OA - where most vulnerable
medial side
OA - nonsurgical treatment - when open vs. closed chain
Acute = open chain
Subacute - closed
Pyogenic arthritis
medical emergency!
Bacterial infiltration
Reiters
reactive arthritis from microbial pathogens
most common in males over 30
ACL injury
Contact or non
Hyperextension, valgus, or rotational force
ACL injury - clinical presentation
audible pop, rapid onset, unable to WB, instability/giving way
Knee flexion as protection
Chondromalacia patellae is what
softening of cartilage on undersurface of patella due to overuse
Special tests for chrondromalcia patellae
Clarke’s
Fat pad syndrome is what
irritation of infrapatellar fat pad due to impingement between femoral condyles and patella
Fat pad syndrome - clinical presentation
Genu recurvatum patella alta hypertrophied fat pad knee cap pain inferiorly titled patella
LCL injury caused by what
Varus stress contact
not as common
heals slowly
LCL - sprain grades
grade 1 = slight
grade 3 = complete tear
Special tests for LCL
varus stress at 0 and 30
MCL injury is caused by what
valgus stress contact with rotational force
often get ACL or meniscus issue too
Meniscus injury is caused by what
trauma with rotation, cutting movement, deep flexion
degeneration (fraying, stable, tears, necrosis, CPPD)
most likely to occur at 30 flexion
Meniscus injury is often associated with what
ACL and MCL injury if caused by trauma
Forced into myperextension can lead to
medial meniscus tear
poor blood supply - poor healing
Clinical presentation with meniscus tear
loacking at 10-30 degrees flexion
instability
click/snap
symptomatic pop with pain at joint line
Special tests for meniscus
Apley joint line palpation valgus/varus stress mcmurray arthrogram mri (not easy to meniscus tear though)
Patellar dislocation caused by what
pivot turn and patella will dislocate
can be direct blow to knee or indirect patellar malalignment
Patella subluxation
More common than dislocation
F more than M
Clinical presentation - sublux
tenderness around patellar border Q angle more than 20 Instability click/slide/lock atrophy of VMO hypertrophy of VL
Patellar tendon rupture caused by
forceful eccentric contraction
defect in inf pole
more common 20-40
PCL injury how
post tibial translation - MVA with tibia on dash
varus, twisting motion
Pre-patella bursitis
prolonged kneeling or falling onto knees
Ottawa rules
Age 55+ Tender fibular head Isolated patellar tenderness Unable to flex knee to 90 Unable to WB for 4 steps immediately post trauma or in ER
Pittsburgh rules
Age less than 12 or more than 50
Unable to walk 4 WB steps in ER
Distal femur fx types
A = extraarticular B = unicondylar C = bicondylar
Femoral shaft fracute -
life threatening because of considerable bleeding and fat embolism
massive force required
Intercondylar (tibial spine) fracture
direct blow to proximal tibia with knee flexed or in rotation
Hyperextension with varus/valgus stress
Bakers cyst
herniated synovial lining
Osgood Schlatters
due to overuse in young athletes
osteochondritis of tibial tubersotiy apophysis
Osteochrondritis dissecans
trauma causes separation of cartilage and subchondral bone
piece becomes necrotis
loose body in joint space
