A single giant geode at the olecranon in a patient with rheumatoid arthritis (RA) is relatively rare, and may cause diagnostic difficulties or cause a spontaneous pathological fracture owing to weakness of the cortical bone associated with osteoporosis. We report two cases of patients presenting with single giant geodes at the olecranon. In one case we performed an open reduction and internal fixation with bone grafting for a pathological fracture due to the geode. In the other case we performed curettage of the geode with bone grafting to prevent a pathological fracture, and a synovectomy of the elbow. We suggest that the presence of a giant geode at the olecranon may necessitate surgical intervention to prevent the occurrence of a spontaneous pathological fracture.