Villonodular synovitis (pigmented), right knee

This code represents pigmented villonodular synovitis (PVNS) affecting the right knee. PVNS is a rare, benign, proliferative disorder of the synovial membrane, characterized by villous and nodular growth with hemosiderin deposition, leading to joint pain, swelling, and effusion. It can be locally aggressive and cause bone erosion.

Use this code when documentation confirms a diagnosis of pigmented villonodular synovitis specifically located in the right knee. This diagnosis is typically made based on clinical presentation, imaging studies (MRI often shows characteristic hemosiderin deposits), and confirmed by synovial biopsy.

• Ensure laterality is clearly documented; if the left knee is affected, a different code is required.
• Distinguish from other forms of synovitis (e.g., infectious, inflammatory) which have different codes.
• Code any associated complications, such as joint effusion or bone erosion, separately if documented.