Transient synovitis, left knee

This code signifies a temporary, non-infectious inflammation of the synovial membrane lining the left knee joint. It is characterized by acute onset of pain, swelling, and limping, typically resolving spontaneously within days to a few weeks. This condition is most common in young children.

Apply this code when documentation clearly indicates a diagnosis of transient synovitis affecting the left knee. This diagnosis is often made after excluding other more serious causes of knee pain, such as septic arthritis or fracture, through clinical examination and imaging. Supporting documentation should include laterality and the transient nature of the condition.

• Ensure documentation specifies "left knee" to support this laterality-specific code.
• Differentiate from other forms of synovitis (e.g., M65.862, Other specified synovitis, left knee) which may be chronic or due to other etiologies.
• Do not use for traumatic effusions or other specific knee derangements; those have their own distinct codes.