Rad Knee

Sinding Larsen Johansson Dx AKA:

"Jumpers Knee"

PATELLA ALTA/BAJA Patient Demographic:

Variable

does the dorsal aspect of the femoral condyles have cartilage?

Yes, all the way from the patella to the dorsal aspect - covers a large area on femoral condyles

Frontal vs Intercondylar view:

Frontal - knee is extended so small "tunnel" between condyles Intercondylar - knee is bent so much larger "tunnel" between condyles

Arthrodesis =

Joint Fusion (congenital block vertebra cause congenital arthrodesis)

Arthroplasty =

Joint Replacement (Arthro - joint) (Platy - replacement)

Patellar Position Projection:

Lateral Knee

How to best evaluate Osgood Schlatter Disease:

Lateral Knee Projection

Os Fabella:

• Anomalous sesamoid bone in lateral head of gastrocnemiustendon • Incidental finding • Seen on frontal and lateral views (os means ossicle)

Sinding Larsen Johansson Dx Radiography:

• Calcification at inferior pole of patella

Osteochondritis Dissecans Complications/Considerations:

• Early osteoarthritis • Deformed articular surface • Persistent pain

Sinding Larsen Johansson Dx on MRI:

• Edema at inferior pole of patella • Edema at proximal end of patellar tendon • Thickening of patellar tendon

Bakers Cyst (Popliteal Cyst) Definition:

• Fluid filled cyst at dorsum of knee • Lined by synovial lining • Connected to joint via gastrocnemius-semimembranosus bursa • Capsular swelling -> excess synovial fluid that decompresses into a cyst

Pellegrini Stieda Dx Findings:

• Focal calcification along MCL

Osteochondritis Dissecans Findings:

• If osteochondral fragment: Contour deformity to articular surface • If chondral fragment: MRI needed to show chondral defect

Knee Lines of Mensuration:

• Insall-Salvati Ratio • Patellar Position

Lipohemarthrosis (FBI Sign):

• Intra-articular fxs create a fat-fluid level secondary to a bloody effusion from marrow leaking into joint • bone marrow extrudes into the jt fluid=> fat floats on sup surface => *• FBI sign (fat, blood, interface)* • cross table lateral of the knee is necessary to demonstrate the fat -fluid accumulation in the suprapatellar bursa

More Knee Abnormalities:

• Lipohemarthrosis • Chondromalacia Patella • OsGood Schlatters Dx • Sinding Larsen Johansson Dx • Pellegrini Stiedas Dx • Bakers Cyst • Osteochondritis Dessicans

Bakers Cyst (Popliteal Cyst) Complications/Considerations:

• May self resolve • drainage,steroid injection common Tx • Can rupture

How to best evaluate Bakers Cyst (Popliteal Cyst):

• Not seen on x-ray • MRI depicts cyst

Osgood Schlatter Disease Definition:

• Partial disruption of the infrapatellar ligament resulting in pain • Strong quads pulling on immature bone/cartilage of tibial tuberosity

Knee Anomalies:

• Patella Alta/Baja • Bipartite/tripartite/multipartite Patella • Os Fabella • Cyamella

Bakers Cyst (Popliteal Cyst) DDX:

• Popliteal artery aneurysm

Pellegrini Stieda Dx Definition:

• Post-traumatic calcification of the medial collateral ligament (MCL)

How to best evaluate Osteochondritis Dissecans:

• Radiography less sensitive than MRI • Common at knee(mc) and ankle

Cyamella:

• Rare anomalous sesamoid bone within the popliteus tendon usually visualized on the lateral aspect of the distal femur in the popliteal groove • Incidental finding • Best seen on AP view

Sinding Larsen Johansson Dx Etiology:

• Repetitive microtrauma to attachment of patellar tendon to patella • Traction tendonitis

Osgood Schlatter Disease Findings:

• ST swelling, thickened patellar ligament, blurred infrapatellar fat pad • Irregularity of anterior tibial tuberosity

Osgood Schlatter Disease Complications/Considerations:

• Self-limiting with rest • May leave residual deformity (*swelling is the most consistent finding, would also have tenderness that is worse in extension of the knee*)

Osteochondritis Dissecans Definition:

• Separation of an osteochondral fragment from the articular surface • Leads to "loose body" chondral or osteochondral fragment • Micro/macro traumatic origin vs focal AVN

Chondromalacia Patella:

• Softening and degeneration of patellar hyaline cartilage • Syndrome of pain and crepitus • MC in young patients (F>M) • Pain exacerbated by prolonged sitting in confined space

Osteochondritis Dissecans Treatment:

• Spontaneous healing possible • If displaced +/- surgery

BIPARTITE/TRIPARTITE/MULTIPARTITE PATELLA:

• Un-united secondary ossification center of patella • *Always in superolateral corner of patella* • May be painful with trauma Incidental Finding: - *Don't Confuse with Fracture* • Best seen on AP projections (BI - 2, Tri - 3, Multi - more than 3) - Bi is one fragment because it is Patella + fragment (2 bones) (Smooth rounded lucencys that ALWAYS happen in the same spot - no history of trauma or pain)

What is the sign called in chondromalacia patella when the pain is exacerbated by prolonged sitting in confined space

*movie sign*

*Why is the medial oblique preferred over the lateral oblique view in the knee?*

*to see proximal tibiofibular joint* (TEST Q) (Lateral has fibula behind the tibia)

Knee Standard Projections:

- AP - Medial Oblique - Lateral

The Knee Bones:

- Femur - Tibia - Fibula - Patella

Patellar Position Significance:

- Patella Alta (superior/high patella) - Patella Baja (inferior/low patella)

What joints have hyaline and fibrocartilage structures:

- Shoulder (labrum and articular cartilage) - Hip (labrum) - Knee (meniscus plus hyaline cartilage)

Knee Accessory Projections:

- Tunnel/Intercondylar - Sunrise/Tamgemtial - Cross Table Lateral

3 Ways the patella fractures:

- Vertical - Horizontal - Stellate (shatter) Should not mix these up with BIPARTITE/TRIPARTITE/MULTIPARTITE PATELLA

Patellar Position Landmarks and Methods:

1. Patellar length: the greatest distance between the sup. and inf. poles of the patella 2. Patellar tendon length: from the inferior pole of the patella to the sup notch of the tibial tuberosity *knee must be flexed*

When do patellas ossify?

3.5-5yo

How to Best Evaluate Pellegrini Stieda Dx:

AP Knee

PATELLA ALTA/BAJA Main Radiographic Findings:

Abnormal Insall-Salvati Ratio Many causes: trauma, surgery, arthritis

PATELLA ALTA/BAJA AKA: None Definition: ?

Abnormal Patellar Position

Ludloff's Spot:

An area where there is a lot of trabecular pattern (normal, no significance) - slide 20 (lateral on distal femur)

Patellar tendon length divided by patellar length =

Insall-Salvati Ratio (Lateral Knee Projection)

What type of imaging modality is best to look at hyaline cartilage?

MRI

Pellegrini Stieda Dx Complications/Considerations:

May be painful

Which condyle appears bigger in the lateral knee projection?

Medial Condyle

Sinding Larsen Johansson Dx has similar etiology to?

Osgood Schlatter Dx

Bakers Cyst AKA?

Popliteal Cyst

Chondromalacia means the cartilage is too ____________

Soft

Which accessory view is the best way to see a patellofemoral joint?

Sunrise (Tangential) View

True or False The tibial tuberosity is a secondary ossification center meaning it will not be ossified in young children

TRUE

Frontal view displays...

Tibiofemoral joint - medial and lateral compartments

What is the point of taking a Cross-Table Lateral for the knee?

To look for lipohemearthrosis (fat and blood in joint)

Malacia means?

To soften