Other instability, unspecified knee

This code describes a general feeling of looseness or giving way in the knee joint, not specified as due to a ligamentous tear or other specific cause. It indicates a functional impairment where the knee does not feel stable during movement or weight-bearing.

Use this code when documentation indicates knee instability without further specificity regarding the underlying etiology or affected ligament. This is appropriate when the physician's assessment notes "knee instability, unspecified" or "other instability of the knee" without identifying a specific ligamentous injury (e.g., ACL, PCL).

• Avoid using this code if a specific ligamentous instability (e.g., M23.5-) is documented; always code to the highest level of specificity.
• Query the provider if the documentation mentions instability but does not specify the knee or laterality.
• This code requires a 7th character for laterality (right, left, or unspecified); the '9' in the provided code indicates unspecified laterality.