Purpose or Case Report: This educational exhibit provides a comprehensive review of normal anatomical variants in the developing pediatric knee, emphasizing the imaging distinctions from pathology to aid radiologists in accurate diagnosis and care.
Methods & Materials: We conducted a literature review on knee development and variants. We explored fetal knee development to understand variant etiology and discussed imaging modalities based on age, skeletal maturity, and clinical indications. Our primary focus was to differentiate normal and pathological variants within three categories: (I) tibiofemoral, (II) patellofemoral compartments, and (III) menisci and ligaments.
Results: In the tibiofemoral compartment, we discuss metaphyseal stripes, distal femoral medial metaphyseal cortical irregularity, and variant ossification of femoral condyles, distinguishing them from pathologic periosteal detachment, malignancy, and osteochondritis dissecans (OCD). In the patellofemoral compartment, we explore bi-/multi-partite patella, dorsolateral defects, inferior patella pole apophysis, and key anatomic landmarks of the trochlea implicated in patellofemoral maltracking, contrasting them with patellar fractures, osteochondral injuries, overuse conditions (Siding-Larsen-Johannsson syndrome and Osgood-Schlatter Disease), and avulsion fractures (patellar sleeve and tibial tubercle avulsions). In the menisci and ligament section, we highlight normal morphology and ligamentous attachments, discussing discoid and ring-shaped morphologies, meniscal flounce, and rarely encountered intra-meniscal ossicles.
Conclusions: Recognizing variations in normal growth and endochondral ossification in the developing pediatric knee is vital, as they may be transient sites of relative weakness and predispose patients to age-dependent injury patterns. It is crucial for radiologists to understand these variants and differentiate them from pathology. Not all normal variants are asymptomatic; some may cause non-specific knee pain and associated injuries. This knowledge is essential for effective patient care and accurate diagnosis.