Ankylosis, unspecified knee

This code describes the pathological fusion or stiffening of the knee joint, resulting in a significant loss of range of motion. This ankylosis is not specified as to its underlying cause, such as trauma, infection, or inflammatory arthritis. It indicates a fixed or severely limited articulation of the tibiofemoral joint.

Use this code when documentation clearly states "ankylosis of the knee" without further specification of laterality or etiology. This diagnosis is typically supported by physical examination findings of severely restricted knee movement and imaging studies confirming joint fusion or severe stiffness. It is appropriate when the specific cause of the ankylosis is unknown or not documented.

• Avoid using this code if the laterality (right or left knee) is documented; instead, select a more specific code from the M24.66- subcategory.
• Do not use this code if the underlying cause of the ankylosis is known and documented (e.g., post-traumatic, rheumatoid arthritis); in such cases, code the underlying condition first, followed by a more specific ankylosis code if applicable.
• This code represents a sequela or chronic condition, not an acute injury.