Osteoid osteoma is very rarely located in the patella,and can represent a significant diagnostic challenge,resulting in a delay of treatment.Patients with osteoid osteoma of the patella often present with knee pain that is also a typical symptom of trauma or of other diseases such as arthritis,which are much more common than osteoid osteoma.We present two young male patients diagnosed with osteoid osteoma of the patella.Each of these patients had a history of intense knee pain; however,accurate diagnosis of osteoid osteoma in the patella had been delayed for more than one year.Computed tomography (CT) scans or magnetic resonance imaging (MRI) showed a circumscribed lesion of the patella in both patients,whereas X-ray examination (posteroanterior projection) was not able to detect the tumor.Different surgical procedures were performed in these patients for resection of the tumors,and the pathology findings confirmed the diagnosis of osteoid osteoma.Both patients recovered completely from surgery.