The Impact of Osseous Erosions on Intraarticular Tenosynovial Giant Cell Tumors of the Knee and Local Recurrence

Background: Tenosynovial giant cell tumor (TGCT) is a rare, mostly benign neoplasm originating in the synovium of joints, tendon sheaths, and bursae that can locally recur after excision and cause osseous erosions. Studies have suggested increased local recurrence with diffuse TGCT, but few have assessed associations of local recurrence or erosions in TGCT of the knee. Our aim was to determine associations of erosions and local recurrence with patient and tumor characteristics in knee TGCT. Materials and Methods: A retrospective chart review was performed on 53 patients with intraarticular, biopsy-proven TGCT of the knee diagnosed at our institution from December 2002 to December 2020. Bivariate analysis assessed the significance of associations between patient and tumor characteristics, surgical management, erosions, and local recurrence. Results: Of 53 patients with intra-articular, biopsy-proven TGCT of the knee, 24 (45%) patients had diffuse, intra-articular TGCT, and 7 (13%) patients had radiographic evidence of osseous erosions. In the diffuse, intra-articular subgroup, 12 (50%) patients had local recurrence, but 5 of 5 patients with erosions had local recurrence. Of the 19 patients with diffuse, intra-articular TGCT without erosion, 7 (37%) had local recurrence ( P = .037). Of the 24 patients with diffuse, intra-articular TGCT, both those who had and did not have local recurrence had similar surgical treatment (75% arthroscopic, 25% open). The average recurrent-free survival was 936 days. Conclusion: Patients with diffuse, intra-articular TGCT of the knee with osseous erosions had a greater incidence of local recurrence than those without. Using erosions as a positive prognostic indicator for local recurrence may assist physicians in risk stratification of patients with diffuse, intra-articular TGCT.