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The Pediatric Knee

Robert C. Orth, M.D., Ph.D.

Edward B. Singleton Department of Pediatric Radiology

Texas Children’s Hospital

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Overview

•Common pediatric developmental variants

•Congenital and developmental abnormalities -Discoid meniscus -Patellar maltracking

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Overview

•Traumatic -Juvenile OCD -Avulsive injuries

•ACL •PCL and popliteus tendon

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Common pediatric developmental variants

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7 year-old girl

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Normal femoral condylar ossification

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Normal femoral condylar ossification

Normal ossification OCD

M=L M>>L

<10 >10

Posterior Middle

No edema Edema

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6 year-old girl

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Distal femoral cortical irregularity

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Distal femoral cortical irregularity

•Benign, self-limited

•Adductor magnus aponeurosis/ medial head of gastrocnemius tendon origin

•Most-commonly 10-15 years-old

•MRI rarely needed

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Posterior metaphyseal stripe

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Posterior metaphyseal stripe

•Distal femur and proximal tibia

•Skeletally immature → normal

•Highly vascular subperiosteal fibrous tissue

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Congenital and developmental abnormalities

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11 year-old girl with 3 months pain Discoid meniscus

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Discoid meniscus

•Lateral >> medial

•Prone to tears and degeneration •Partial or complete •>50% tibial plateau •Painful when not torn

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Wrisberg variant

•Hypermobile

•Only attached by Wrisberg ligament

Woods G W and Whelan. Clin Sports Med. 1990

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Popliteomeniscal fascicles

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11 year-old girl with complete discoid meniscus

Horizontal cleavage tear Parameniscal cyst Radial tear

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Partial discoid meniscus

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16 year-old girl with 2 months anterior knee pain

Superolateral Hoffa’s fat pad edema

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Superolateral Hoffa’s fat pad edema

•Patellar maltracking -Patella alta

-Patellofemoral dysplasia

•Often the only abnormality

•Distinguish from inferior patellar pole avulsion

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3.8 cm

5.6 cm

3.8 cm

5.6 cm

Insall–Salvati ratio

•Patellar tendon: patella length

•Patella alta

-1.3 in males

-1.5 in females

•5.6/3.8 = 1.5

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Parameters associated with patellar maltracking

•Patellofemoral angle (PFA) •Patellar tilt •Trochlear depth •Patellar translation •Tibial tuberosity-trochlear groove distance (TT-TG)

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17-year old injured at wrestling camp Lateral patellar dislocation

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Lateral patellar dislocation

•May not be suspected clinically

•Imaging findings -Edema at medial patellar pole +/- avulsed sleeve fragment

-MPFL or MPR rupture

-Osteochondral defect from trochlea

-Lateral femoral impaction

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16 year old boy with acute pain

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Lateral patellar dislocation with MPFL and MCL tears

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Elias D A et al. Radiology 2002

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Traumatic

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13 year-old boy with 6 months pain

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Pain free following 6 weeks immobilization

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Juvenile OCD versus adult OCD

•Better prognosis

•MR findings of instability less specific -Cysts

-T2 hyperintense rim

-Full-thickness cartilage defect

-Loose body

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10 year-old girl with OCD

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Unstable osteochondritis dissecans

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12 year-old boy with 2 year history of knee pain

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Acute and chronic avulsion injuries

•Osteochondral junction relatively weak -Tendon

-Ligament

•Affects -Cruciate ligaments

-Posterolateral corner

-Extensor mechanism

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9 year-old boy injured playing soccer

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Tibial spine avulsion with intact ACL

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ACL-complex injuries

•Younger -Tibial spine avulsions

-Partial ACL intrasubstance tears

•Compared to adults

-Associated injuries less frequent but common

-Secondary signs similar

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1 cm peripheral tear

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ACL-Tibial angles increase with age

5 yo

11 yo 7 yo

15 yo

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10 year-old girl with tibial spine avulsion

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10 year old boy - injury and swelling

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Complete PCL avulsion

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Posterolateral corner injuries

•Common with PCL-complex injuries

•Provides rotational stability

•Static and dynamic stabilizers -Lateral collateral ligament

-Popliteus muscle and tendon

-Capsule

Harner C D et al. Am J Sports Med. 2000

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12 year-old unable to walk

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Popliteus tendon avulsion

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Summary

•Normal variant ossification versus OCD -Younger -Posterior -No edema

•Discoid menisci

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Summary

•Patellar tracking abnormalities -Superolateral Hoffa’s fat pad edema -Lateral patellar dislocations

•Juvenile versus adult OCD -Better prognosis -Stability difficult to determine

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Summary

•Avulsive injuries -Lateral patellar dislocation

-ACL, PCL, posterolateral corner

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Thank you