Intra-articular Osteoid Osteoma of the Olecranon Fossa.

Osteoid osteomas are benign primary bone lesions characterized by a central nidus with surrounding reactive sclerosis, classically presenting as worsening nocturnal pain relieved by non-steroidal anti-inflammatory medications (NSAIDs). These most commonly occur in intracortical bone and the diaphysis of long bones. As a rare entity, intra-articular osteoid osteomas present unusually, often resulting in a delayed or incorrect diagnosis. We present a case of an intra-articular osteoid osteoma, emphasizing the importance of MRI in aiding diagnosis in this atypical location.

Concomitant lipoma arborescens and synovial osteochondromatosis of the knee.

Intra-articular masses are not a rare finding in routine imaging. This is particularly true in patients with underlying joint diseases such as degenerative arthritis. Nevertheless, concomitant presentation is rather uncommon in imaging studies. The authors report an unusual concomitant lipoma arborescens and synovial osteochondromatosis (which has not previously been reported in the literature to the best of the authors' knowledge) in a man in his 60 s with a long-standing history of knee osteoarthritis. In this case presentation, we review the differential diagnosis for noninfectious synovial proliferative disorders presenting as intra-articular masses, their potential association with underlying joint pathology, and discuss the key imaging features and appropriate treatment.

Case report of intra-articular synovial sarcoma in the hip joint.

Synovial sarcoma is a type of soft tissue sarcoma that commonly occurs around large joints. However, primary intra-articular synovial sarcoma is considered an extremely rare variant of synovial sarcoma. We present a case of synovial sarcoma arising from the hip joint in a 17-year-old female patient. Clinical, radiographic, magnetic resonance imaging and histopathology findings are described. The patient underwent neoadjuvant chemoradiation therapy followed by right hemipelvectomy, and there was no local recurrence in the subsequent follow ups. Unfortunately, the patient had pleural metastasis, and she was treated with palliative chemotherapy. To the best of our knowledge, there is only one published case report in the English literature on intra-articular synovial sarcoma from the hip joint.

Intra-articular post-traumatic ankle joint mass imitating localized pigmented villonodular synovitis (LPVS), the aid of ankle arthroscopy for diagnosis and treatment-a case report.

Intra-articular post-traumatic ankle joint mass is a rare entity that may mimic other pathologies, mainly localized form of pigmented villonodular synovitis (LPVS) regarding the clinical and imaging characteristics. We report the case of a 16-year-old female patient that presented an intra-articular ankle joint mass 8 months after an ankle joint sprain for which magnetic resonance imaging (MRI) suggested LPVS as possible diagnosis due to the presence of hemosiderin deposits. Diagnosis of a post-traumatic hematoma of her ankle joint was made via fine needle aspiration (FNA) biopsy and anterior ankle arthroscopy. At one-year-follow-up after the arthroscopic excision of the hematoma, the patient remained asymptomatic and pain free while MRI revealed no pathologic findings. This case demonstrates that LPVS is not always the diagnosis when hemosiderin deposits are depicted on the MRI of a solitary intra-articular mass. The FNA biopsy under direct arthroscopic view assists the diagnosis and guides the treatment plan in cases that no definite diagnosis has been reached preoperatively by MRI. Level of evidence IV, case report.

A Case of Rheumatoid Arthritis Presenting as an Intra-articular Mass of the Wrist Joint in a Patient with Chronic Monoarthritis

Rheumatoid arthritis (RA) mainly affects polyarticular joints and is characterized by inflammation of the synovial membrane leading to joint destruction. We report on an unusual case of RA presenting as an intra-articular mass invading bone of the wrist joint in a patient with chronic monoarthritis. A 43-year-old man presented with left wrist joint pain and swelling lasting several years. A plain radiograph showed a non-specific osteolytic lesion in the distal ulna but a magnetic resonance image demonstrated an intra-articular irregular mass-like lesion with eccentric bone erosion the distal radioulnar joint. Synovial biopsy detected hyperplasia of the synovial lining cell layer and finger-like protrusions of inflamed and edematous fibrovascular stroma containing dense inflammatory infiltrates, mainly plasma cells, B cells, and CD4+ T cells. Rheumatoid factor and anti-citrullinated protein antibody were highly positive. The patient was diagnosed with RA and treated with disease-modifying anti-rheumatic drugs, showing a good response on further follow-up.