Background: We report the removal of a large metallic foreign body and review the relevant literature. Methods: A 28 y old woman was admitted with left knee swelling, pain, and limitation of activity resulting from an accident 7 d earlier. Radiography revealed a 3 × 1 cm foreign body at the mid-tibial plateau. As the foreign body may have been metallic, it was not possible to perform magnetic resonance imaging to determine whether damage to the cruciate ligaments was present. Finally, the foreign body was retrieved. Results: A 3 × 4 × 5 cm triangular broken knife blade was removed from the joint cavity. We excised the lateral meniscus, which had been damaged by the foreign body, and debrided the hyperplastic synovial membrane. Recovery was favorable with no complications. The patient was followed up at 6 months after surgery. Conclusions: While foreign bodies in the knee are not uncommon, the presence of a large object is rare. When foreign bodies are small, most can be removed arthroscopically with a minimum of difficulty. In contrast, large foreign bodies within the knee joint cavity require an incision to open the joint for adequate exposure and removal of the object. Such a procedure can result in severe complications, such as infections and joint deformities. The decision to use one or the other approach requires careful consideration regarding the condition of the patient along with the skill, knowledge, and experience of the health care team.

Rationale:Desmoplastic fibroma (DF) is a rare, locally invasive but benign bone tumor. It represents one of the rarest bone diseases, with an incidence of only 0.11% of all primary bone tumors.Patient concerns:Herein, a case of massive and unusual DF, with simultaneous involvement of ilium and ischium, is described. A 29-year-old man suffered minor pain in his right hip for 2 years. It worsened after sudden movements, which prevented him from walking normally. Physical examination showed a limitation when the right hip was flexed and a percussion pain on the hip region. A medical imaging examination showed that the right ilium and ischium had a massive bone lesion. The top of acetabular had very little bone left and a fracture was likely at any time. No prominent body weight loss was noted, because there was no extensive invasion to the adjacent soft tissue.Diagnoses:DF of the Ilium and Ischium.Interventions:The patient underwent a surgery involving curettage and grafting to maintain the stability of the pelvis.Outcomes:The definitive pathological diagnosis was DF, without evidence of malignancy. The postoperative recovery course at 3-month follow-up was uneventful.Lessons:To the authors’ knowledge, such a massive DF involving both ilium and ischium has been rarely reported. Young patients require appropriate and timely treatment modalities.