Yes, 27422 would still be the correct code for the procedure done by your surgeon even though the "reticular disruption" was found 3 months post TKR. By that time, the problem had become "chronic." Even if it had been identified earlier in the postoperative period I would probably use the same code. The others you refer to, 27405 for Primary Repair of Torn Ligament of the Knee is designated as applying to "collateral" ligaments, which would not include the medial retinacular disruption, and 27427 for Ligamentous Reconstruction/Augmentation of the Knee, Extra-articular, also is restricted to the Collateral &/or Cruciate Ligaments. These really don't apply to Patellar Instability/Malalignment/Maltracking problems/surgery.
Unfortunately, some of the procedures and procedural names for treating Patellofemoral Disorders have gone by the wayside and replaced with newer terminology, but are still referenced in the CPT Codes. You will not see your surgeon doing a Hauser, Goldwaite, or Campbell Procedure. These have been replaced by newer terminology such as Proximal (Soft Tissue) Realignment (27422) and Distal Realignment (27420) as in my earlier discussion. You may very well see the "Fulkerson Procedure," which a Distal Realignment, by your surgeon. This does involve an osteotomy of the Tibial Tubercle, plus some/other elements of the Proximal Realignment as discussed. This is the "updated" version of the Hauser Procedure.
As for "Reconstruction of the Medial Patellofemoral Ligament" procedure, this is a relatively recently developed procedure (5-10 years) which is done arthroscopically for the most part or with very limited open exposure. I have to be honest to say that I do not know whether it has been given a CPT Code of its own yet.
Again, I hope this all helps. This is a very complex issue and territory of knee surgery, and unfortunately the code descriptors in CPT have not been updated to reflect current thinking and vernacular.
Respectfully, Alan Pechacek, M.D.