Comparison of Weightbearing and Nonweightbearing Juvenile Osteochondritis Dissecans Lesions of the Lateral Femoral Condyle

BACKGROUND: Repetitive microtrauma may contribute to osteochondritis dissecans (OCD) lesions of the femoral condyle. The effect of differential loading between OCD weightbearing (WB) zones has not been studied. PURPOSE: To determine whether clinical and radiographic variables differ by WB zone in lateral femoral condyle OCD lesions. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: We retrospectively reviewed a consecutive series of patients aged <18 years with lateral femoral condyle OCD lesions presenting at a single institution between 2004 and 2018. Patients with OCD lesions outside of the lateral femoral condyle were excluded. Lesions were localized on radiographs using the Cahill and Berg classification, referencing the Blumensaat line and an extension of the posterior femoral cortex. Progeny bone characteristics evaluated at baseline and 24-month follow-up included ossification, distinct borders from parent bone, and displacement. Baseline lesion dimensions were measured on magnetic resonance imaging (MRI) scans. We evaluated posttreatment pain level, return-to-activity rate, and patient-reported outcome measures (PROMs) including the Pediatric International Knee Documentation Committee score, Knee injury and Osteoarthritis Outcome Score, and Pediatric Functional Activity Brief Scale. RESULTS: A total of 62 lateral femoral condyle OCD lesions (mean follow-up, 24.1 months) presented within the study period: 26 WB lesions and 36 nonweightbearing (NWB) lesions. At presentation, no differences between the lesion types were observed in symptom chronicity or symptomatology. NWB lesions were deeper on MRI scans (sagittal depth, 7.11 vs 5.96 mm; P = .046; coronal depth ratio, 0.05 vs 0.01 mm; P = .003), were more likely to develop progeny bone (69.4% vs 44%; P = .047), and demonstrated higher radiographic healing rates (52.8% vs 24%; P = .025) compared with WB lesions. PROMs at follow-up were available for 25 of 62 patients (40.3%), with no statistically significant differences between cohorts at any time. Return to full activity was observed in 72% of WB and 82.1% of NWB lesions (P = .378). CONCLUSION: Lateral femoral condyle OCD lesions of the knee in WB and NWB zones presented similarly at initial evaluation; however, NWB lesions demonstrated higher rates of progeny bone formation and radiographic healing at mean 2-year follow-up.