Other specified crystal arthropathies, unspecified knee

This code signifies an inflammatory joint condition of the knee caused by the deposition of crystals other than urate (gout) or calcium pyrophosphate (CPPD). It represents a form of crystal-induced arthritis where the specific crystal type has been identified but does not fall into the more common categories.

Use this code when documentation specifies crystal arthropathy of an unspecified knee, and the crystal type is identified as something other than monosodium urate or calcium pyrophosphate dihydrate. This typically occurs after synovial fluid analysis or biopsy confirms the presence of unusual crystal formations.

• Ensure the documentation explicitly states "other specified crystal arthropathy" and specifies the knee as the affected joint.
• Avoid using this code if the crystal type is identified as urate (gout) or calcium pyrophosphate (CPPD); use the more specific codes for those conditions.
• If the specific knee (right or left) is documented, use the more precise anatomical site code (M11.861 or M11.862).