Transient synovitis, unspecified knee

This code describes a temporary, non-infectious inflammation of the synovial membrane lining the joint capsule of an unspecified knee. It is characterized by acute onset of knee pain and limping, often without a clear traumatic cause, and typically resolves spontaneously within a few days to weeks.

Use this code for patients presenting with acute, self-limiting knee pain and effusion where diagnostic workup rules out other causes like infection, trauma, or chronic inflammatory conditions. Documentation should indicate "transient synovitis" and specify the affected knee as "unspecified" if laterality is not documented or not applicable.

• Ensure documentation explicitly states "transient synovitis" and does not indicate a chronic or infectious process.
• Avoid using this code if a more specific diagnosis, such as traumatic synovitis or a specific inflammatory arthropathy, is identified.
• If laterality (right or left knee) is documented, use the more specific M67.361 or M67.362 codes.