Knee and Femur Flashcards
What are the clinical indications for the knee?
trauma
bony tenderness at thehead of thefibula
isolated patella tenderness
patient unable to flex the knee to 90 degrees
if the patient is unable to weight bear
suspectedosteoarthritis
detectingjoint effusions
infection
What are the clinical indications for the femur?
trauma
obvious deformities
suspected foreign body
inability to weight bear
osteomyelitis
What is the criteria of the Ottowa Knee Rules?
Age > 55 years
Isolated tenderness of the patella (no other bony tenderness)
Tenderness at the fibular head
Unable to flex knee to 90°
Unable to bear weight both immediately and in ED (4 steps, limping is okay)
If any of the criteria are met, this patient may need knee imaging: the rule is sensitive to rule-out fractures, but not specific to suggest who may have a fracture.
When do the Ottowa Knee Rules apply?
all patients aged 2 and older with knee pain/tenderness in the setting of trauma.
What are the routine projections for the knee?
AP and Lateral
What are the routine projections for the femur?
AP and Lateral
How do you tell adequacy for an AP knee X-Ray?
Femoral and tibial condyles should be symmetrical
Fibula Head is slightly superimposed by the lateral tibial condyle
Patella is on the superior portion of the image superimposing the distal femur.
How do you tell adequacy for a Lateral Knee X-ray with horizonal beam?
superimposition of the medial and lateral condyles of the distal femur
patellofemoral joint spaceopen
slight superimposition of the fibular head with the tibia
How do you tell adequacy for an AP femur X-ray?
The whole femur should be seen on the image: the long axis of the femur should run parallel to the long axis of the image
Greater trochanter seen in profile = adequate internal rotation of the limb
May require 2 images – proximal and distal structures
How do you tell adequacy for a Lateral Femur X-Ray?
greater and lesser trochanters should be superimposed by the femoral neck
a small part of the lesser trochanter is visible medially
anterior and posterior margins of the femoral condyles should be superimposed
May require 2 images – proximal and distal structures
What are the additional projections for the knee?
Lateral Knee (rolled)
Axial
Skyline Merchant View
Skyline Laurine View
Rosenburg View (Tunnel)
How is the patient’s knee positioned in a lateral knee x-ray?
Pt. lies on side of interest with the knee of interest closest to the table and the other lower limb rolled anteriorly
affect knee is flexed slightly ≈ 30° (to the best of patient’s ability)
if the medial adductor tubercle is not superimposed, projecting posteriorly in the image rotate the kneeexternally.
If the lateral condyle significantly superimposes the medial adductor tubercle the knee must beinternallyrotated.
What is the skyline merchant view of axial knee x-ray?
superior-inferior projection of the patella
patella should be free from superimposition of all bony structures
clear visualisation of the patellofemoral joint space
What is the skyline Laurine view of axial knee x-ray?
Inferior-superior projection of the patella
The knee is flexed 20-30 degrees.
Ensure the patient’s feet are out of the primary beam.
The X-rays pass inferior to superior through the patella
patella should be free from superimposition of all bony structures
clear visualisation of the patellofemoral joint space
What is the Rosenburg view (tunnel) of the knee?
knees slightly bent to around 45 degrees
The x-ray beam is angled 10-20 degrees caudad
tibial plateau should be free from any superimposition
femoral condyles should be free from superimposition
intercondylar fossa in profile, giving the appearance of a ‘notch’
Why do we assess the radiograph with lines of measurement?
to evaluate normal and abnormal skeletal relationships
What are the lines of measurements used in knee x-ray?
Insall-Salvati ratio (Patella Position)
Tibiofemoral alignment
What is the Insall-Salvati Ratio (Patella Position)?
The ratio between the length of the patella tendon and the length of the patella
Length of patella ligament = Distance from tibial tuberosity to apex of patella
Length of the patella = Distance form the apex to the base of the patella
Knee flexed to 30°Lateral projection
Ratio of 0.8 – 1.2 - normal
Ratio <0.8 (Patella Baja) - low lying patella
Ratio >1.2 (Patella Alta) - high lying patella
What is Patella Baja (<0.8)?
quadriceps dysfunction:
poliomyelitis
tourniquet paralysis
bony or ligamentous trauma:
fractures
osteotomies
tibial tubercle transplant
ACL repair
total knee replacement: seen in 25% of patients
achondroplasia: usually asymptomatic
What is Patella Alta (>1.2)?
idiopathic retropatellar pain
recurrent dislocation of the patella
chondromalacia patellae
knee joint effusion
PFPS – PatelloFemroal Pain Syndrome
Osgood–Schlatter’s Disease,
Sinding-Larsen-Johansson Disease
patellar tendonitis
What is Tibiofemoral alignment for the knee/femur?
AP Knee
Draw a line down the lateral margin of the lateral femoral condyle
Line >5mm lateral of lateral tibial plateau = tibial plateau fracture!
What are anatomical variants, congenital and acquired abnormalities of the knee/femur?
Nail Patella/Fong’s Syndrome
Sesamoid Bones
Fabella
Cyamella
Bipartite/Tripartite Patella
Ludloff’s Patch
Osgood-Schlatters Disease
Sinding-Larsen-Johannsen Disease
Pellegrini-Stieda Lesion
Tug Lesion
What is Nail Patella Syndrome/Fong’s Syndrome?
Rare genetic condition which results from symmetrical mesodermal and ectodermal abnormalities
caused by genetic changes (pathogenic variants ormutations) in theLMX1Bgene.
The syndrome isinheritedin anautosomal dominantmanner
fragmented/absent/hypoplastic patellae, enlarged tibial tuberosity
What is the Os Fabella in the knee?
Sesamoid bone - bone withing a tendon or muscle
Typically found in the lateral head of the gastrocnemius, occasionally found medially
Found in an average of 20% of the population
Form in response to strain
Anatomical variant
Os Fabella - Can be fibrocartilaginous in nature, not just bony
lateral knee; Small, round, bony structures with smooth cortical margin posterior to the femoral condyles
limited blood supply - prone to avascular necrosis
