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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