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)
1.1.1.1 Group Osteoarthritis of knee (M17)
1.1.1.1.1 Diagnosis Bilateral primary osteoarthritis of knee (M17.0)