Radiological Study of Ossified Fabella in Indian Knees: A Cross-sectional Study

Abstract

Introduction: The fabella is a sesamoid bone found in the posterior and lateral region of the knee, identified on X-rays behind the femoral condyle in a true lateral view. Occasionally, it is a source of knee pain and is associated with radiological evidence of osteoarthritic knees. Due to its uncommon occurrence, there are very few studies related to an ossified fabella. While posteromedial pain and varus are common entities in knee arthritis, attention needs to be given to posterolateral structures like the fabella, as its radiological appearance may indicate the presence of arthritis. Aim: To determine the occurrence of the fabella and its association with arthritis and knee deformities, such as varus or valgus, in Indian knees on X-rays. Materials and Methods: This was a single-centre, X-ray-based, cross-sectional study conducted in the Joint Replacement Unit-II of the Department of Orthopaedics between June 2022 and March 2023 at KLE's Dr. Prabhakar Kore Hospital in Belagavi, Karnataka, India. A total of 500 knees were radiologically studied using Medsynapse/Picture Archiving and Communication System (PACS), and Cohen's Kappa Test statistics were employed to measure the agreement between the radiologist and orthopaedician regarding the presence or absence of the fabella interpreted on X-rays. Results: The occurrence of ossified fabella was observed in 87 (17.4%) subjects. Amongst these 27 (31.03%) had bilateral fabella, while remaining 60 (68.97%) had it either on left or right side. There was a high association between the occurrence of the fabella with age, Osteoarthritis (OA), and knee deformity (p-value0.05). Conclusion: The study revealed that ossified fabella is significantly associated with knee OA, age, and knee deformities.

Keywords

• osteoarthritis
• posterolateral
• sesamoid bone
• varus
• x-ray