Dear "Daedolos":
In ICD-10, by definition the M Codes are for Disorders of the Musculoskeletal System that are not the result of an Injury, for which the S Codes apply. The S Codes appear to apply to only Acute and Subacute injuries, i.e. present now as a result of a recent traumatic episode. This is indicated by the Exclusion of "current injury" by many M Codes when there is a question as to the origin of a chronic disorder, such as an old ligamentous injury and instability, or the possibility of an old meniscal tear that may have at one time been an acute injury. M Codes can be used for Acute and Subacute disorders except current injury, such a Acute Tendonitis, Bursitis, Joint Pain, and others (congenital/developmental). The problem is that not all "Chronic Musculoskeletal Problems/Disorders" are purely degenerative in nature/origin, but may be the long term result of an old injury (such as Post-traumatic Arthritis, M15-M19). And, "Old Injuries" can lead to/result in "Chronic Disorders," with progression over time. An old traumatic meniscal tear may not be a significant enough clinical problem as to require surgical intervention early on, but over time may do so gradually or suddenly/acutely, without necessarily being the result of a "current injury." This doesn't even allow for an "Acute on Chronic" coding possibility/opportunity. ICD-10 does very poorly at accommodating these different possibilities, particularly in the area of ligamentous and/or meniscal disorders in the knee. I addressed/discussed this dilemma in my Blog on coding knee pain problems, and gave my recommendations and thoughts there.
For example, the M23 Code Set, Internal derangement of the knee, Excludes(1) currentinjury of the knee and lower leg (S80-S89). The M24 Code Set, Other specific joint derangements, which has some codes relevant to the knee, also Excludes(1) current injury of the knee ... as well. The S83 Code Set Excludes(1) the codes in M22, M23, and M24 code sets that apply to the knee and patella. Even more specific is that S83.2 pertaining to meniscal tears Excludes(1) M23.0, M23.2, and M23.3.
Unfortunately I don't know how to resolve these issues. I have some ideas, but not the clout nor the where-with-all to get changes made with CMS. For example, there is no need for both Code Sets M23.2 and M23.3. These could be simplified to one set for Old/Chronic and Other Meniscal Tears/Derangements, including degenerative, old traumatic, or "other," with 5th Characters of 1 through 6 as described already, and 6th Character for laterality. As for Chronic Instability of the Knee (M23.5), this could be
expanded to include from Old Ligamentous or Other Injury. This would allow for the expansion of the code set with 5th Characters for the different types of instability (anterior, posterior, medial, lateral, rotary, and multiple and/or complex ligament injuries, and their synonyms). This would be better than trying to get the knee (5th Character 6) included in M24.2 _, which has no room for this expansion.
I am sorry you are having to deal with Aetna. I am no expert on insurance companies, and have never liked of any of them, but by history and reputation in the Medical Provider realm, Aetna is the worst. They will bend, turn, twist every rule or interpretation they can their way so as to not pay for care. So what you tell me is no surprise. However, surgical treatment of a chronic meniscal tear (degenerative, old traumatic, or otherwise) is not "experimental" if the patient's clinical problem is well/clearly explained by the meniscal tear, and the indications for surgical treatment of the tear are documented, i.e. Medical Necessity is fulfilled. I wish I had some good advise as to how to deal with them.
I don't know if any or all this helps, but I agree and commiserate with you on these problems.
Sincerely, Alan Pechacek, M.D.