Intermittent hydrarthrosis, unspecified shoulder

This code signifies recurrent, spontaneous effusions into the shoulder joint without an apparent underlying cause like trauma or infection. The joint swelling is typically intermittent, resolving and recurring over time, and is often associated with pain and limited range of motion.

Apply this code when documentation explicitly states "intermittent hydrarthrosis" affecting an unspecified shoulder. This diagnosis is typically made after excluding other causes of joint effusion through clinical examination, imaging, and laboratory tests.

• Ensure the documentation specifies "intermittent" and not a chronic or acute effusion with a known cause.
• If the laterality of the shoulder is documented (right or left), use the more specific codes M12.411 or M12.412.
• Do not confuse with other forms of synovitis or arthropathy where a specific etiology is identified.