Stiff fingers and fastenings that get in the way
Short answer: Choose garments without buttons, hooks and zips. Elastic, large openings and stretchy fabric solve most of it.
What is difficult
Small buttons, hooks at the back of the neck and zips with a small pull require fine motor control and force. If fingers are stiff in the morning, those three things take the longest and cause the most trouble.
The alternatives that work
Trousers with a soft elastic waist instead of button and zip. Tops that pull over the head or have large buttons. Bras that fasten at the front or have no hooks. See bamboo bras without underwire.
Stretchy fabric makes a difference
A garment with a little elastane can be stretched over the hand rather than requiring a fastening to be opened. See bamboo sweatpants for men and bamboo underwear for women.
Frequently asked questions
Are there aids for this
Yes, there are button hooks and zip pulls. An occupational therapist can show which ones suit.
What about socks
A sock with a wide opening and some stretch is the easiest. Sock aids also exist.
Are magnetic fastenings an option
They exist on some clothing and can be easier than buttons for stiff fingers.