The stapes is the stirrup-shaped small bone or ossicle in the middle ear which is attached through the incudostapedial joint to the incus laterally and to the fenestra ovalis, the "oval window", medially. Stapes means stirrup in Latin. The oval window is adjacent to the vestibule of the inner ear. The stapes is the smallest and lightest bone in the human body. It was described by the professor Giovanni Filippo Ingrassia in 1546 at the University of Naples. - Wikipedia

There are many e.g. over 30 small joint surfaces in the wrist and hand. It is hard to say. Answer The smallest bony joint in the skeleton is found within the head. It is that between the two ossicles incus and stapes.

There are 2 stirrups on each saddle. One hangs down on either side. The stirrups give you a place to rest your feet while riding. This adds some security and helps the rider keep their balance. Experienced riders do not need stirrups in order to stay on, however stirrups do make it easier and less tiring.

A stirrup in a english, western and aussie saddle help the rider to balance and hold on. From Walking all the way to high jumping stirrups help the rider with their balance which also helps the horses balance.

The following information is provided to prevent the continuing deaths from persons being dragged after getting their foot caught in the stirrup during a fall: It is life-saving to make sure that the stirrup fits so closely to the rider's boot both in width and height so that it is not possible for the rider's foot to fit through the stirrup. This is to prevent the rider from getting their foot caught in the stirrup during a fall and being dragged literally to death. Stirrups are available in different widths and heights. Make sure you buy ones that do not allow your foot to go all the way through. Elastic sided so called "safety stirrups" unfortunately do allow the rider's foot to go all the way through and so allow for the rider to get caught on the remaining L-shaped steel part of the "safety stirrup" and therefore are very un-safe. The only safe stirrup is one that is fitted too closely to your foot to allow your foot to go through it, while at the same time is not so tightly wrapped around your foot that your foot cannot get out of it. The stirrup must fit each person individually and be bought in the correct size for that individual person, not simply bought in size "child's stirrup" or size "adult stirrup", but must be measured to match the rider's boot in inches or centimeters where the ball of the foot would rest on the stirrup. Riders wear boots with heels to help prevent the foot from going through the stirrup but the boot-heel by itself is not enough to completely prevent that problem. Test the stirrup by trying to put your foot through it in any way you can while you are not on the horse. If you can get your foot through it, it is the wrong stirrup due to either wrong size or wrong overall shape or both. (Not every saddle is provided with hinged safety bars to allow the stirrup leather resting on them to come off during a fall, and, some of the hinged safety bars are too rusted to un-hinge)