Drug-induced chronic gout, unspecified knee, with tophus

This code signifies a chronic inflammatory arthritis caused by medication, specifically affecting an unspecified knee joint, and characterized by the presence of urate crystal deposits (tophi). The drug-induced nature differentiates it from primary gout.

Apply this code when documentation clearly states chronic gout in the knee is a direct result of drug therapy, and tophaceous deposits are noted. This diagnosis requires a physician's explicit statement linking the gout to a specific medication.

• Ensure documentation specifies "drug-induced" and the presence of "tophi" in the knee.
• Do not use for acute drug-induced gout or chronic gout without tophi.
• Code the specific drug causing the adverse effect using an external cause code (T36-T50) as a secondary diagnosis.