Index Maintenance on Clustered PK Index

I know there are similar question to this one, but I couldn’t find one dealing with Index Maintenance…

I have some PK Clustered Indexes [int (auto increment).] I always notice that these Indexes frequently have two issues:

  1. Fragmentation is quickly over 10%
  2. Fragmentation is sometimes over 90%

Do I need to apply the same logic (REBUILD/REORGANIZE) to these indexes?