Background: Pigmented villonodular synovitis (PVNS) is a rare proliferative process in children that mostly affects the knee joint.
Case presentation: The study follows the case of a 3-year-old boy presenting recurrent patellar dislocation and PVNS. Due to symptoms such as chronic arthritis, he had been taking prednisolone and methotrexate for 6 months before receiving a definitive diagnosis. After a period of showing no improvements from his treatment, he was referred to our center and was diagnosed with local PVNS using magnetic resonance imaging (MRI). The patient was treated for his patellar dislocation by way of open synovectomy, lateral retinacular release, and a proximal realignment procedure, with no recurrence after a 24-month follow-up.
Conclusion: PVNS may appear with symptoms resembling juvenile idiopathic arthritis, thus the disease should be considered in differential diagnosis of any inflammatory arthritis in children. PVNS may also cause mechanical symptoms such as patellar dislocation. In addition to synovectomy, a realignment procedure can be a useful method of treatment.
Keywords: Juvenile idiopathic arthritis; Patellar dislocation; Pigmented villonodular synovitis.