MRI findings of chondroblastomas of the knee: preferential physeal involvement with tibial lesions

Abstract Objective To characterize the spectrum of MRI findings of chondroblastomas of the knee and location-dependent differences. Materials and methods This IRB-approved retrospective study included pediatric patients (< 18 years) with pathologically confirmed chondroblastoma about the knee and available preoperative MRI (2008–2025). All MRI examinations were retrospectively reviewed to characterize lesion volume, anatomic location, margin characteristics, marginal low signal intensity rim, internal fluidlike signal and fluid levels, epiphyseal and metaphyseal marrow edema, and cortical and physeal involvement. Location-dependent differences were investigated using the Fisher exact and Mann–Whitney U tests. Results Twenty-four patients (median age 15.0 years, IQR 13.7–16.3; 21 boys, 3 girls) had 13 distal femoral and 11 proximal tibial lesions of similar size ( p = 0.93). Proximal tibia lesions were more likely than distal femur lesions to have transphyseal extension (72.7% vs. 23.1%, p = 0.04); metaphyseal marrow edema accompanied all transphyseal lesions ( p = 0.02), whereas physeal maturity did not differ between groups ( p = 0.21). Otherwise, most chondroblastomas had lobulated margins (83.3%), an extensive low signal intensity rim (62.5%), extensive epiphyseal marrow edema (54.2%), and cortical involvement (75.0%), with common internal fluidlike signal (70.8%) but uncommon fluid level (29.2%) and no other significant differences between sites. At median follow-up of 24 months (IQR 14.0–25.7), only a minority (8.3%) had surgically confirmed local recurrence, and one patient (with a proximal tibial lesion, 4.2%) developed growth disturbance. Conclusion Knee chondroblastoma demonstrates a characteristic spectrum of MRI findings; transphyseal extension is more common with proximal tibia than distal femur lesions.