Case Report
Copyright ©The Author(s) 2021. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Clin Cases. Feb 26, 2021; 9(6): 1379-1385
Published online Feb 26, 2021. doi: 10.12998/wjcc.v9.i6.1379
Subtalar joint pigmented villonodular synovitis misdiagnosed at the first visit: A case report
Wen-Qian Zhao, Bin Zhao, Wan-Sheng Li, Isaac Assan
Wen-Qian Zhao, Department of Traditional Chinese Medicine, The People's Hospital of Shouguang City, Shouguang 262700, Shandong Province, China
Bin Zhao, Department of Orthopedics, Shouguang Hospital of Traditional Chinese Medicine, Shouguang 262700, Shandong Province, China
Wan-Sheng Li, Department of General Surgery, Shouguang Hospital of Traditional Chinese Medicine, Shouguang 262700, Shandong Province, China
Isaac Assan, School of International Education, Weifang Medical University, Weifang 261053, Shandong Province, China
Author contributions: Zhao B and Zhao WQ contributed to conceptualization of the study; Zhao B aided with the surgery; Zhao WQ, and Li WS contributed to the data curation; Zhao B wrote the original draft; Assan I contributed to the article review, edit, and diction analysis; All authors issued final approval for the version to be submitted.
Informed consent statement: Informed written consent was obtained from the patient for publication of this report and any accompanying images.
Conflict-of-interest statement: The authors declare that they have no conflicts of interest.
CARE Checklist (2016) statement: The authors have read the CARE Checklist (2016), and the manuscript was prepared and revised according to the CARE Checklist (2016).
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:
Corresponding author: Bin Zhao, MD, Attending Doctor, Department of Orthopedics, Shouguang Hospital of Traditional Chinese Medicine, No. 3353 Shengcheng Street, Shouguang 262700, Shandong Province, China.
Received: September 17, 2020
Peer-review started: September 17, 2020
First decision: November 26, 2020
Revised: December 8, 2020
Accepted: December 23, 2020
Article in press: December 28, 2020
Published online: February 26, 2021

Pigmented villonodular synovitis (PVNS) is an uncommon disease that usually occurs in large joints, and involvement of the subtalar joint is rare. The lack of comprehensive knowledge of subtalar joint PVNS could lead to misdiagnosis.


We present a 64-year-old woman who, at her first visit, complained of discomfort in the right ankle when she walked. Based on the physical signs and X-ray report, the physician failed to make the suspected diagnosis of PVNS. Eighteen months later, the patient returned with a complaint of a mass in her right lateral malleolus with intermittent blunt pain. The X-ray presented an osteophyte formation and soft tissue calcification at the margin of the subtalar joint. The laboratory tests were normal, whereas magnetic resonance imaging (MRI) showed a low-intensity area on both T1- and T2-weighted images. A suspected diagnosis of PVNS was made and later confirmed by postoperative pathology. Subsequently, the patient received radiotherapy with 32 Gy in 16 fractions. At 6 mo postoperatively, the patient only complained of discomfort after walking three blocks. The American Orthopedic Foot and Ankle Society Ankle–Hindfoot score was 97.


MRI is necessary for the diagnosis of PVNS. Early soft tissue calcification and painless joint swelling should be of concern.

Keywords: Pigmented villonodular synovitis, Subtalar joint, Steinmann pin retractor, Case report, Tenosynovial giant cell tumor

Core Tip: Diffuse subtalar joint pigmented villonodular synovitis (PVNS) is a rare disease that can potentially cause bone and cartilage lesions if misdiagnosed at an early stage. Magnetic resonance imaging should be recommended if a physician is suspicious of PVNS. We present a case of misdiagnosed PVNS to improve our understanding of the early characteristics of diffuse subtalar joint PVNS.