Standard Knee SeriesStandard Knee Series

• AP Knee

• Lateral Knee

• Tunnel Knee

AP Knee

• pt is positioned with 15o of internal rotation of the foot

• femorotibial joint spaces should measure between 5-11 mm

Lateral KneeLateral Knee

• approximately 30-35 degrees of flexion of the knee

Blumensaat’s lineBlumensaat’s line

• Dense white line representing the surface of the intercondylar notch that is tangential to the x-ray beam.

Ludloff’s Ludloff’s PatchPatch

• A lucency in the distal distal femoral femoral epiphysisepiphysis

• best seen around the age of 16 years

3 year male

• The ossification center for the patella is first apparent.

• normal patellar ossification does not begin until 1.5-5 years years of ageof age

• The patellar ossification center is more prominent, and a normal pronounced indentation is evident at the anterior portion of the tibia at the eventual site of the tibial tubercle.

5 year male

Patellar PositionPatellar Position

• Patella AltaPatella Alta - patellar ligament greater than 20% longer than the patella

• Patella BajaPatella Baja - patella positioned too low

the greatest length of the patella and the length of the the greatest length of the patella and the length of the patellar tendon (ligament) should be equal (20% patellar tendon (ligament) should be equal (20% variation is acceptable)variation is acceptable)

Tunnel KneeTunnel Knee

• approximately 45o of knee flexion and a 45o caudad tube tilt

Accessory ProjectionsAccessory Projections

Tangential Tangential Patella Patella

• aka Sunrise Patellaaka Sunrise Patella• lateral vs medial

patellofemoral joint space

Lateral Medial

Bilateral AP Weightbearing Bilateral AP Weightbearing KneesKnees

Oblique Oblique KneeKnee

Normal Variants of the KneeNormal Variants of the Knee

Patella agenesis

• Rare.• Usually associated

with hereditary osteo-onychodysostosis.

Nail Patella Syndrome AKA Nail Patella Syndrome AKA Fong’s Syndrome, HOOD Fong’s Syndrome, HOOD

syndromesyndrome• hypoplastic or absent

patella• nail abnormalities• may see kidney

dysfunction and webbing of the elbow

• iliac hornsiliac horns• elbow abnormalitieselbow abnormalities

Harris LinesHarris Lines

• aka Growth Arrest Growth Arrest LinesLines

• represents areas of growth arrest resolution

Bipartite Bipartite PatellaPatella

• bilateral 80% of the time

Tripartite Tripartite PatellaPatella

Os Os CyamellaCyamella

• accessory ossicle in the popliteus popliteus tendontendon

Os FabellaOs Fabella

• sesamoid bone located within the tendon of the lateral head of lateral head of the the gastrocnemius gastrocnemius musclemuscle

• bilateral in 2/3 to 3/4 of individuals

Dorsal defect of the patella

• Variant in ossification.• Circular radiolucent

defect in superolateral pole of patella.

• May simulate neoplasm.• May be related to

bipartite patella.

• Self limiting.• Incidental finding in

children.

Osgood-Osgood-Schlatter’s Schlatter’s

DiseaseDisease

• m/c in males • 11 - 15 years of age

• fragmentation of the tibial tuberosity

Sinding-Larsen-Sinding-Larsen-Johannsen Johannsen SyndromeSyndrome

• inferior pole of the patella

Pellegrini-Pellegrini-SteidaSteida

• calcification of the medial collateral medial collateral ligamentligament

• usually follows previous trauma

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