Derang of post horn of lat mensc d/t old tear/inj, unsp knee

This code signifies a structural disruption of the posterior aspect of the lateral meniscus, resulting from a prior injury or degenerative process. It indicates an internal derangement of the knee joint, specifically affecting the shock-absorbing cartilage on the outer side. The "unspecified knee" denotes that laterality (left or right) is not documented.

Apply this code when documentation confirms a chronic or old tear of the posterior horn of the lateral meniscus, leading to ongoing symptoms such as pain, clicking, or locking. This diagnosis is appropriate when the physician's notes explicitly state "old tear," "chronic derangement," or "due to prior injury" without specifying the affected knee.

• Ensure the documentation clearly states "old tear" or "due to old injury" to differentiate from acute tears.
• Avoid using this code if the laterality (left or right knee) is specified; instead, use the more specific codes for left (M23.251) or right (M23.252) knee.
• Do not use for acute meniscal tears; refer to the M23.3- series for acute derangements.