Long-term functional outcomes of diffuse pigmented villonodular synovitis of the knee after synovectomy with or without adjuvant radiotherapy

Background: Diffuse pigmented villonodular synovitis (PVNS) of the knee is a rare benign disease that has a destructive clinical course. Reported treatment options include arthroscopic or open synovectomy with or without adjuvant radiotherapy of various doses. This study compared the long-term functional outcomes and disease control among treatment modalities and discussed 22 years of experience with radiotherapy (RT) as an adjuvant treatment for PVNS of knee.Methods A single-center database was searched for patients who received synovectomy of knee with the pathologic diagnosis of PVNS. General data, treatment modalities, and recurrent status were retrospectively collected from medical records. Functional outcomes were evaluated by Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) through phone interviews by an independent orthopedist.Results From January 1995 to December 2017, 24 patients with diffuse PVNS of knee were identified, including 19 receiving open synovectomy (OP) and 5 undergoing arthroscopic surgery (AS). Adjuvant RT was performed on 14 patients with a median dose of 34.25 Gy (range 20-40 Gy). After median follow up of 6 years, clinically or radiographically confirmed recurrences were recorded in 10 cases. The local recurrence rate was significantly lower in the OP+RT group than the OP group (8.3% vs. 57.1%, p =0.038). Among those with preserved knee joints, there was no significant difference in the WOMAC score and stiffness score between patients in the OP+RT and OP groups.Conclusions In conclusion, for patients with diffuse PVNS of knee, the addition of moderate-dose adjuvant RT to open synovectomy provided excellent local control while maintaining good joint function with limited treatment-related morbidity. Our study emphasized the importance of moderate dose of RT in diffuse PVNS of knee joint.