It depends on the type of prosthetic!
Most prosthetics are static, with legs being the most common example. The majority of prosthetic legs are basically well-engineered, very ergonomically-designed wearable crutches. The wearer can’t control them much, beyond moving whatever body part it’s attached to.
Some people have prosthetic hands/arms that are completely passive/immovable — just there for cosmetic reasons or general comfort/balance.
Okay, **moving on to more advanced prosthetics with movable appendages.** The most common ways that prosthetics can move are:
– Manual, lockable prosthetics. For example, an elbow that can be moved (e.g. manually with your other hand) into a bent position and then locked so that you can carry something.
– Cable-controlled prosthetics. For a long time this was the most advanced sort of upper limb prosthetic we had. The prosthetic is hooked up to a harness that the wearer puts on, which allows them to control the prosthetic through small movements of the body (especially the opposite shoulder). Small movements pull on cables to, for example, open or close a prosthetic hand.
– The most modern prosthetic technology includes prosthetics that can be controlled by…well, basically, leftover nerves. [These are super new and not very widely available.](https://www.michiganmedicine.org/health-lab/its-you-have-hand-again) Some very smart scientists figured out how to hook up prosthetics to leftover nerves in the upper limbs of partial amputees. This allows the wearer to control the prosthetic with their brain — the brain sends signals to the nerves, which tells the prosthetic what to do. Just like how you tell your arm and hand what to do!
There are a lot of other, more specialized types of prosthetics out there. Many folks who use prosthetics have multiple options depending on what they are doing — for example, a different prosthetic leg for exercising vs going to work.
It’s a rapidly evolving field!
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