There is a principle that applies not only too the human body but also to anything with moving parts . When there is too much movement there can be PAIN !!!!
When the deep stabilisers or reflexive stabilisation system is not firing our joints will not be cent rated and supported allowing the global system to operate without any anchor point.
Often precise movement education is needed to restore the stabilisers.
The home exercise could also have been in a supine position if sitting was too difficult . Sorry about the shaky picture my wrist was MOVING TOO MUCH.