Are Fibrous Cortical Defects (FCDs) and Non-Ossifying Fibromas (NOFs) Only Radiological Findings? The Relationship between Radiological/Clinical Findings and Physical Activity in Children and Adolescents: A Cross-Sectional Study

<b>Background:</b> Fibrous cortical defect (FCD) and non-ossifying fibroma (NOF) are incidentally recognised and benign developmental lesions. The objective of this study was to ascertain the clinical manifestations and symptoms of FCDs/NOFs in children and adolescent patients, to characterise the lesions radiologically using X-ray and MRI techniques, and to determine the relationship between physical activity and the condition. <b>Methods:</b> The study included patients under the age of 18 with radiological lesions on their extremities. The lesions were classified as FCD or NOF in accordance with the distinctive imaging features. For each lesion, the bone involved, the site involved, the size of the lesion, and the type of lesion (according to the Ritschl classification) were recorded. In the anamnesis, the patient's presenting complaint, the character of the pain, if any, and the level of activity were investigated. Pain was quantified using the visual analogue scale (VAS) and the 21-Numbered Circle VAS (21-NCVAS). The 21-Numbered Circle Activity Scale (21-NCAS) and the International Physical Activity Questionnaire (IPAQ) were employed for the assessment of physical activity. <b>Results:</b> The study included 34 lesions in 28 children (14 girls/14 boys). There was no difference in age between girls and boys (<i>p</i> = 0.45). According to Ritschl's classification, 18 (52.9%) lesions were stage A, 9 (26.5%) were stage B, and 7 (20.6%) were stage C. The lesion size increased with increasing Ritschl stage (<i>p</i> < 0.02). The main presenting complaint was pain (n = 13, 49.9%). In 21.4% of the children (n = 6), lesions were detected incidentally on radiographs. According to IPAQ, 39.3% of the children were physically inactive. There was a significant negative correlation between 21-NCAS and Ritschl stage (r = -0.51, <i>p</i> < 0.05). Activity decreased as the Ritschl stage increased. There was a significant negative correlation between 21-NCAS and VAS (r = -0.69, <i>p</i> < 0.05). <b>Conclusions:</b> Spontaneous pain was observed in 49.9% of patients diagnosed with FCD/NOF. No correlation was identified between lesion size and the presence or severity of pain. As the severity of pain and Ritschl stage increased, there was a corresponding decrease in physical activity.