Villonodular synovitis (pigmented), left knee

This code identifies pigmented villonodular synovitis (PVNS) affecting the left knee. PVNS is a rare, benign, proliferative disorder of the synovial membrane, characterized by villous and nodular growths, hemosiderin deposition, and often causing joint pain, swelling, and effusion. It can lead to significant joint destruction if left untreated.

Apply this code when documentation confirms a diagnosis of pigmented villonodular synovitis specifically located in the left knee joint. Supporting documentation should include imaging reports (e.g., MRI showing synovial proliferation and hemosiderin) and/or pathology reports from synovial biopsy confirming PVNS.

• Ensure the laterality is explicitly documented as "left knee" to support this specific code.
• Distinguish from other forms of synovitis or arthropathy; PVNS has distinct pathological features.
• If the PVNS is diffuse or localized, this code applies to both presentations within the left knee.