en Orthopedic Surgery Orthopedic Surgery Original Research Original Research <p> <strong> Background </strong>:Pigmented villonodularsynovitis (PVNS) is characterized by the presence of inflammation and hemosiderin deposition in the synovium. Two forms of PVNS distinguished in the literature are diffused and localized involvements. There are controversies in the literature about the surgical management of PVNS. We report our experience in the management of knee PVNS at a mean follow-up of 4 years. We also introduce our preferred method of treatment for these patients. </p><p> <strong> Methods </strong>: A number of 26 patients (26 knees) with histologically proven PVNS of the knee in the pathology department at ShafaYahyaeyan hospital were identified between January 1996 and February 2012. Annual clinical follow-up was conducted in all patients and a follow-up MRI scans was ordered for symptomatic cases. All patients were examined according to the Knee Society Score (KSS) in which the knees were graded from excellent to poor. </p><p> <strong> Results </strong>: Mean age of the patients was 28.08±12.5. A number of 15 patients (58%) had diffused involvement of the knee joint and 11 (42%) had a localized form of involvement. Mean follow up was 4 years. The mean duration of symptoms prior to presentation was 44.40±38.69 months. In five cases (23%) subtotal synovectomy and in 21 cases (77%) total synovectomy was performed. Two cases (7.7%) had recurrence. In a comparison between new methods vs. routine methods, after adjusting the pre-operation KSS scores, there was a significant difference between both methods in their post-op results. There were no complications in the form of knee instability, infection or neurovascular injury. </p><p> <strong> Conclusion </strong>: The PVNS of knee joint especially the diffused form should be carefully observed and managed using appropriate investigations. Staged open total synovectomy with a posterior and then an anterior approach seems to be a superior method for surgical treatment of diffused forms. </p><p>  </p> Knee joint, Pigmented VillonodularSynovitis, Synovectomy, Recurrence. 815 822 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-1569-5&slc_lang=en&sid=1 Mahmoud Jabalameli jabalamelimd@yahoo.com 200319475328460013817 200319475328460013817 No Head of Knee Department, ShafaYahyaeyan Hospital, Iran University of Medical Science, Tehran, Iran. Khodamorad Jamshidi jamshidi_k@yahoo.com 200319475328460013818 200319475328460013818 Yes Head of Bone Tumor and Oncologic Surgery Department, ShafaYahyaeyan Hospital, Iran University of Medical Science, Tehran, Iran. Mehran Radi meh_radi@yahoo.com 200319475328460013819 200319475328460013819 No Knee Surgery fellow, ShafaYahyaeyan Hospital, Iran University of Medical Science, Tehran, Iran. Hosseinali Hadi hosseinali_hadi@yahoo.com 200319475328460013820 200319475328460013820 No ShafaYahyaeyan Hospital, Arak University of Medical Science, Arak, Iran. Abolfazl Bagherifard bagheri@meph.ir 200319475328460013821 200319475328460013821 No ShafaYahyaeyan Hospital, Iran University of Medical Science, Tehran, Iran.