Uncommon Cause of Knee Pain in Behçet’s Disease: Suprapatellar Synovial Chondromatosis

Abstract

A 44-year-old male patient with Behcet’s disease presented to our clinic with progressively worsening right knee pain and suprapatellar swelling. The knee pain started about a month previously and increased over time. The characteristic of the pain was mechanical. He did not feel pain while sleeping. Previously, he had received analgesic medications but there had been no significant improvement. There was no pain in any other joint, and there was no history of disease or trauma and arthritis attack associated with the knee. The patient had a history of Behcet’s disease for five years and patient was using colchicine 3x1 pozology a day. On physical examination there was no arthritis findings. Patella shock test was negative. The patient was seen to have visibly swollen suprapatellar area. On palpation the swelling was hard, non-mobile, well defined, and measured 2x1 cm. Radiography of the knee indicated multiple soft tissue calcifications outside the joint capsule of the right knee. Knee magnetic resonance imaging revealed expanded sinovium that contained osteochondromas, which were hypointense all sequences (Figure 1). The patient’s blood tests were normal. Arthroscopic debridement were performed with symptomatic right knee joint. Pathology results were evaluated as synovial chondromatosis (SC). SC is a rare arthropathy of unknown etiology. The disease is generally monoarticular, usually occurs unilaterally in the large joints like the knee, hip, and elbow (1). Primary or idiopathic form may occur in an otherwise normal joint, but secondary SOC may occur due to trauma or degenerative diseases. On the other hand, it may occur in the setting of preexistent osteoarthritis, rheumatoid arthritis, osteonecrosis, osteochondritis dissecans, neuropathic osteoarthropathy, tuberculosis, or osteochondral fractures (2,3). To the best of our knowledge, the suprapatellar SOC of the knee in a Behcet disease is rare, and this encouraged us to report this case. Secondary SC should be included in the differential diagnosis of Behcet disease’s joint pain.