Proximal tibia chondroblastoma mimicking an osteochondral defect treated with trapdoor, curettage, cryoablation, grafting and suture osteosynthesis.

Chondroblastomas are uncommon bony neoplasms that can present similarly to other benign lesions, such as osteochondral lesions. We report a case of an 18-year-old male with a chondroblastoma in the left medial proximal tibia epiphysis, initially misdiagnosed as a benign osteochondral lesion. The patient presented to the clinic with left knee pain that impacted his active lifestyle. Initial examination and imaging favoured a benign osteochondral lesion, which was treated arthroscopically. However, persistent symptoms led to further investigations, suggesting the diagnosis of a chondroblastoma. An open bone biopsy with a medial trapdoor approach, curettage, local adjuvant treatment with dehydrogenated alcohol and nitrogen bone chips with filling of the bony cavity using HydroSet® (Stryker Portage, MI, USA) bone substitute was performed. At the 3-year follow-up, the patient remained symptom-free with no recurrence. This case highlights the challenges in differentiating between these lesions and provides valuable insights into their diagnosis and management.