The purpose of the study was to assess the outcomes of knee synovectomies in children with juvenile idiopathic arthritis. Thirty-one arthroscopic synovectomies were performed in 19 children (six oligoarthritis, 20 polyarthritis, five psoriatic arthritis). The percentage of recurrence in the group with oligoarthritis was 67%, in the group with polyarthritis was 95%, whereas all psoriatic arthritis recurred. The overall mean survival (i.e. free from recurrence) was 1.05 years (95% confidence interval, 0.74–1.35). Mean survival time was 1.69, 0.80 and 1.30 years, respectively, for oligoarthritis, polyarthritis and psoriatic arthritis. After synovectomy we observed two complications: thrombophlebitis of the omolateral superior femoral vein and septic arthritis. In conclusion, the mainstay of therapy for juvenile idiopathic arthritis remains medical treatment and intensive physiotherapy. The aim of arthroscopic synovectomy is to allow to make the most of nonsurgical therapy. It revealed more accurate and less invasive results than open synovectomy, maintained the range of motion of the joint, allowed early mobilization and required shorter hospitalization. Best results were observed in the group of oligoarthritis.