Prevalence and Clinical Impact of Accessory Ossicles of the Knee (Os Fabella and Os Cyamella) in the Indian Population: A Radiographic Observational Study

Abstract Background: Accessory ossicles of the knee, particularly the os fabella and os cyamella, are developmental variants that may affect biomechanics, mimic pathology on imaging, and contribute to knee pain, especially in degenerative conditions. Data on their prevalence and clinical relevance in the Indian population are limited. Objectives: To determine the prevalence, radiographic characteristics, and clinical impact of os fabella and os cyamella in an Indian population using bilateral knee radiographs. Materials and Methods: This radiographic observational study included 1000 adults (≥18 years) undergoing standardized bilateral knee radiography at a tertiary care teaching hospital in Western India over 2 years. Anteroposterior and lateral radiographs were assessed for fabella and cyamella, including laterality and morphology. Osteoarthritic changes were recorded. Knee pain and posterolateral knee pain were correlated with radiographic findings. Chi-square test was applied, and P < 0.05 was considered statistically significant. Results: Accessory ossicles were identified in 364 patients (36.4%). Fabella was the most common (360, 36.0%), while cyamella was rare (20, 2.0%). Fabella prevalence increased with age, reaching 63.6% in individuals >60 years. Bilateral fabella was frequent (16.0%). No association with gender was observed ( P = 0.28). Patients with accessory ossicles had a higher prevalence of knee pain (37.4% vs. 25.8%; P = 0.006), posterolateral knee pain (19.8% vs. 9.1%; P < 0.001), and radiographic osteoarthritis (42.3% vs. 27.7%; P < 0.001). Conclusion: Accessory ossicles of the knee are common in the Indian population and are significantly associated with age, knee pain, and osteoarthritic changes.