Idiopathic chronic gout, left knee, without tophus (tophi)

This code signifies a persistent, long-term form of gout affecting the left knee, where the underlying cause is unknown (idiopathic). Importantly, there is no evidence of tophi, which are deposits of uric acid crystals, associated with this specific presentation.

Apply this code when documentation clearly indicates a diagnosis of chronic gout in the left knee without an identifiable secondary cause, and the absence of tophaceous deposits. Supporting documentation would include physician notes detailing the chronicity of the condition, location, and specific mention of "idiopathic" and "without tophi."

• Ensure documentation explicitly states "idiopathic" and "without tophus" for the left knee.
• Distinguish from acute gout (M10.-) and other forms of chronic gout (M1A.-) that may have a known cause or involve tophi.
• If the laterality is unspecified or bilateral, a different code from the M1A.00 series would be more appropriate.