Bilateral synovial chondromatosis in the knee joint with both intra and extra-articular diseases

Synovial chondromatosis is a rare disease of unknown etiology. It usually occurs unilaterally in the large joints like the knee, but may occur in the shoulder, elbow, hip, ankle and temporomandibular joints. The disease is usually intracapsular, but can also be extracapsular on rare occasions. The diagnosis of synovial chondromatosis is given after an anamnesis, physical examination and radiographic examination. However, the diagnosis is obtained after histological examination of the synovial tissue. We report an unusual presentation of bilateral synovial chondromatosis in the knee joint, with both intra and extracapsular localization. never described in the literature. Although synovial chondromatosis is described as a benign disease, it can be very destructive and debilitating. These lesions can mimic a malignant tumor and present a diagnostic problem.


Introduction
A synovial chondromatosis is a rare benign neoplasm that is caused by metaplasia of the synovium into chondrocytes [1]. The aetiology of the disease is uncertain. Milligram classified the disease into three phases: early(active intrasynovial disease but no loose bodies), transitional disease (active disease and loose bodies), and late (multiple loose bodies but no intrasynovial disease) [2]. The disease is commonly mono-articular and mostly affects the knee [3]. It occurs twice as frequently in men than women and usually presents with increasing joint pain and swelling during the third to fifth decade of a patient's life. A patient with synovial chondromatosis experiences a decreased range of motion, palpable swelling,effusion, and crepitus [4]. The disease is usually intracapsular, but can also be extracapsular on rare occasions [5].
In this case report, we describe a patient with both intra-and extraarticular diseases affecting both knees. To the best of our knowledge, this is the first case with such an extensive presentation of intra and extra-articular disease affecting bilateral the knee joint. surrounding it on the right one (Figure 1, Figure 2). Although some of these appeared to lie within the capsule, the majority appeared to be outside of it, and a solitary image on the left knee ( Figure 3, Figure 4). These appearances were thought to be consistent with idiopathic tumoral calcinosis. However, to further scrutinize these calcifications, a magnetic resonance imaging (MRI) scan was recommended. It showed an extensive thickening of the patient's synovium, multiple intraarticular calcific and ossific loose bodies, and large calcified bursal extensions. These findings were thought to be consistent with very extensive bilatéral synovial chondromatosis.

Patient and observation
The patient's blood tests were normal: C-reactive protein 5 mg/l and the phosphate calcium balance without errors. A two-stage procedure was planned following the findings of the MRI scan. The

Discussion
Synovial chondromatosis is a rare benign condition characterized by the presence of cartilaginous nodules in the synovium of joints, tendon sheaths, and bursae which often occur without trauma or inflammation [1]. With disease progression, the loose bodies may ossify and can be identified radiographically [6]. There are a variety of names for this lesion. The most commonly accepted include synovial chondromatosis, synoviochondrometaplasia, synovial chondrosis, synovial osteochondromatosis, and articular chondrosis [6]. The condition is generally thought to be monoarticular and over Page number not for citation purposes 3 50% of reported cases occur in the knee [7]. Extra-articular synovial chondromatosis is rare, but the combination of intra-and extraarticular diseases described here is an extremely rare condition.
Given the initial X-ray image of large extra-articular calcification,we felt that the patient was more likely to have idiopathic tumoral calcinosis. However, tumoral calcinosis usually only affects people from Africa and the Caribbean in their second decade of life [8].
Extra-articular diseases can be classified as tenosynovial chondromatosis or bursal chondromatosis depending on the origin [9].
It is generally agreed that the exact aetiology of synovial chondromatosis is unknown and controversy exists surrounding Advanced imaging, such as CT and MRI scans are useful in identifying and localizing the lesions as well as helping to distinguish between other differential diagnoses. Blood tests and arthritis profiles can also help rule out specific differential diagnoses. As radiotherapy and chemotherapy have no effect on synovial chondromatosis, surgical excision is the preferred treatment [4]. In cases that involve localized intra-articular disease, complete excision of the abnormal synovium seems to provide a cure. Generalized intra-articular disease with pain and swelling requires total synovectomy and a removal of the loose bodies. Extra-articular disease treatment aims for complete excision [8].

Conclusion
This case is reported because of its rarity.

Competing interests
The authors declare no competing interest.

Authors' contributions
All authors have read and agreed to the final version of this manuscript and have equally contributed to its content and to the management of the case.