Ultrasound-Guided Synovial Biopsy in Chronic Knee Monoarthritis: A Case Series Highlighting Its Diagnostic Value.

Ultrasound-guided synovial biopsy represents a valuable diagnostic tool in the investigation of chronic knee monoarthritis, particularly in cases where conventional clinical, laboratory, and imaging findings remain inconclusive. We report a case series of three patients presenting with chronic knee monoarthritis evolving over several months who were managed in a tertiary rheumatology center. In all cases, ultrasound-guided synovial biopsy was performed after inconclusive routine investigations and enabled definitive etiological diagnosis. Histopathological examination revealed two cases of osteoarticular tuberculosis and one case of localized pigmented villonodular synovitis, thereby allowing timely and targeted therapeutic management. This case series highlights the diagnostic accuracy, safety, and reproducibility of this minimally invasive technique and emphasizes its potential role in reducing diagnostic delays and improving patient outcomes.