The t-sql below will retrieve the fragmentation on the indexes for a database named DATABASENAME. You will want to replace 'DATABASENAME' with the name of your database.
Use DATABASENAME GO SELECT OBJECT_NAME(i.object_id) AS TableName ,i.name AS TableIndexName ,phystat.avg_fragmentation_in_percent FROM sys.dm_db_index_physical_stats(DB_ID(), NULL, NULL, NULL, 'DETAILED') phystat inner JOIN sys.indexes i ON i.object_id = phystat.object_id AND i.index_id = phystat.index_id WHERE phystat.avg_fragmentation_in_percent > 10
You can also use the PowerShell Script here: How to quickly check the health of your Nintex Workflow SQL Indexes
Once the fragmentation has been found you can plan accordingly for reorganizing/rebuilding the indexes. The link below provides further information on how to reorganize/rebuild these indexes.