The reason I wanted to change the nesting it is because I wanted to use the official ICD 10 - WHO standard.
1 Diagnosis Set of Sets
1.1 Chapter Diseases of the musculoskeletal system and tissue (M00-M99)
1.1.1 Section Osteoarthritis (M15-M19)
184.108.40.206 Group Osteoarthritis of knee (M17)
220.127.116.11.1 Diagnosis Bilateral primary osteoarthritis of knee (M17.0)
Generally it is not a good UI decision to ask clinicians to navigate an ICD hierarchy. Please see Load ICD-10 in spanish for diagnostics for a discussion about use of interface terminology. Clinicians are not coders. If you want a coding workflow we should probably discuss using the reference_terminology tables.