VOL. 96-B, No. 8, AUGUST 2014 1111  ONCOLOGY Functional outcome and quality of life after the surgical treatment for diffuse-type giant- cell tumour around the knee A RETROSPECTIVE ANALYSIS OF 30 PATIENTS L. van der Heijden, M. J. L. Mastboom, P. D. S. Dijkstra, M. A. J. van de Sande From Leiden University Medical Center, Leiden, the Netherlands  L. van der Heijden, MSc, MA, PhD Student  M. J. L. Mastboom, BSc, Medical Student  P. D. S. Dijkstra, MD, PhD, Consultant Orthopaedic Surgeon  M. A. J. van de Sande, MD, PhD, Consultant Orthopaedic Surgeon Leiden University Medical Center, Department of Orthopaedic Surgery, Postzone J11-R70, PO Box 9600, 2300 RC Leiden, the Netherlands. Correspondence should be sent to Ms L. van der Heijden; e-mail: lvanderheijden@lumc.nl ©2014 The British Editorial Society of Bone & Joint Surgery doi:10.1302/0301-620X.96B8. 33608 $2.00 Bone Joint J 2014;96-B:1111–18. Received 9 December 2013; Accepted after revision 23 April 2014 We retrospectively reviewed 30 patients with a diffuse-type giant-cell tumour (Dt-GCT) (previously known as pigmented villonodular synovitis) around the knee in order to assess the influence of the type of surgery on the functional outcome and quality of life (QOL). Between 1980 and 2001, 15 of these tumours had been treated primarily at our tertiary referral centre and 15 had been referred from elsewhere with recurrent lesions. The mean follow-up was 64 months (24 to 393). Functional outcome and QOL were assessed with range of movement and the Knee injury and Osteoarthritis Outcome Score (KOOS), the Musculoskeletal Tumour Society (MSTS) score, the Toronto Extremity Salvage Score (TESS) and the SF-36 questionnaire. There was recurrence in four of 14 patients treated initially by open synovectomy. Local control was achieved after a second operation in 13 of 14 (93%). Recurrence occurred in 15 of 16 patients treated initially by arthroscopic synovectomy. These patients underwent a mean of 1.8 arthroscopies (one to eight) before open synovectomy. This achieved local control in 8 of 15 (53%) after the first synovectomy and in 12 of 15 (80%) after two. The functional outcome and QOL of patients who had undergone primary arthroscopic synovectomy and its attendant subsequent surgical procedures were compared with those who had had a primary open synovectomy using the following measures: range of movement (114º versus 127º; p = 0.03); KOOS (48 versus 71; p = 0.003); MSTS (19 versus 24; p = 0.02); TESS (75 versus 86; p = 0.03); and SF-36 (62 versus 80; p = 0.01). Those who had undergone open synovectomy needed fewer subsequent operations. Most patients who had been referred with a recurrence had undergone an initial arthroscopic synovectomy followed by multiple further synovectomies. At the final follow- up of eight years (2 to 32), these patients had impaired function and QOL compared with those who had undergone open synovectomy initially. We conclude that the natural history of Dt-GCT in patients who are treated by arthroscopic synovectomy has an unfavourable outcome, and that primary open synovectomy should be undertaken to prevent recurrence or residual disease. Cite this article: Bone Joint J 2014; 96-B:1111–18. Tenosynovial giant cell tumours are classified as being either localised or diffuse. 1 In this study we focused on the diffuse type (Dt-GCT, previously known as pigmented villonodular synovitis), which is a benign but locally aggres- sive tumour with the capacity for autonomous growth and invasion of bone. The presence of chromosomal aberrations suggests a neoplastic rather than a reactive origin. 2 Dt-GCT devel- ops in the synovial lining of joints, tendon sheaths and bursae. 3 It is mostly mono-articular and involves the knee in 75% of cases, the hip in 15%, and other sites such as the ankle, elbow and shoulder in 10%. It often involves the entire synovium, and there may be an asso- ciated extra-articular infiltrative soft-tissue mass. It affects the genders equally and occurs mainly between the ages of 30 and 40 years. Dt- GCT is usually assessed with MR imaging, and the surgical approach is planned accordingly. Its incidence is estimated at two per million annually 1,4 but this may be an underestimate, as awareness of the disease is growing and diag- nostic methods are improving. Patients present with non-specific symptoms such as pain, lock- ing, a limited range of movement of the joint and a haemorrhagic joint effusion. 1,5 There may be a delay of years between the onset of the dis- ease and its diagnosis. 5 Treatment options for Dt-GCT around the knee include arthroscopic or open synovec- tomy, intra-articular radioactive colloids, radi- otherapy, targeted systemic therapy, or a combination of these. 6 Currently, surgery