Osage, like other Siouan languages and other American languages, has a set of instrumental markers (in Osage, prefixes) to specify the method or means the action described by the verb was achieved with. Morphologically, these instrumental prefixes are divided in 'outer' instrumentals (occurring before, or outside inflection) and 'inner' instrumentals, which occur between pronominal inflection markers and the verb root. The use of an inner instrumental makes an intransitive verb transitive. They are more frequent in Osage than outer instrumentals.
Cf. the linked instrumental morphemes. Most commonly, instrumental markers take patient and agent inflection to the left, e.g. _ðuu, _kaa.
The instrumental ðii ~ ðuu 'by hand' is, or can also be employed as a causative marker. It can also mark adjectives or adjectival verbs (Quintero 2004: 202); cf. examples with ðuutáahpa 'make round', ðuuwásu 'cleanse', or ðuuhkĩhkĩ 'make curly'.
In Quintero, the instrumental kaa 'by striking' appears as a special case, in which kaa is suppressed for persons 1st and 2nd in the verb paradigm, similar to dative inflection. Moreover there exist verbs which appear to be formed with kaa, but where semantically kaa as an instrumental doesn't make sense. Moreover, in those cases, according to Quintero inceptive ki blocks kaa. I am suspecting a historically distinct source for the last described occurrence of kaa which is not related to instrumental kaa and semantically distinct. What Quintero calls "kaa instrumental verbs" have own agent an patient inflection paradigm particularities and in my view must be treated separately from instrumentals. Examples with kaa verbs therefore in this database are not filed under instrumentals, but separately, under accusative kaa.