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 Try the following trick (not recommended for people with a balance or movement disorder): Stand up. Close both your eyes. Balance on one foot (this part is optional, if you prefer) and then touch the tip of your nose with both index fingers. Did you fall over? If you did, you may have a problem with proprioception. If you didn’t, proprioception is why not.
Proprioception
The word “Proprioception” is a combination of the Latin proprius, meaning “one’s own”, and “perception.” It is a perception of self or, more accurately, a perception of where your body is and what it’s doing; the sense you have of where your limbs are in relation to each other. The traditional senses (sight, smell, touch, taste and hearing) are essentially external: They collect information from the outside world. Other senses, such as balance and proprioception, collect information from the body*.
Muscle Feedback
Proprioception occurs because the nerve pathways that travel from your brain to your muscles are two-way: Orders go out along one set of nerves, and proprioception goes back along another. Proprioception allows you to pick up a remembered object without looking at it, to walk without looking at your feet, to move in the dark without falling over, and to accurately kick a football while looking at it and not your feet (although that may depend upon how much training you’ve had!)
Many people have experienced temporarily impaired proprioception as a result of moderate to severe alcohol poisoning. The above trick, minus the standing on one leg, is called the Field Sobriety Test in America and is used by police officers to assess degree of drunkenness. Subjects with impaired proprioception due to a high blood-alcohol level are more likely to stab themselves in the eye, provided they stay upright.
Far-reaching consequences
Permanently impaired proprioception can impact upon every aspect of your life, and may require rigorous retraining as compensation.
The reason proprioception is so important is that it is not just limited to the large skeletal muscles, as the above examples might suggest: In order to speak, your brain needs to use proprioception to keep track of where your jaw and tongue are and what shape your throat is. In order to drive, you need to be able to move the steering wheel, the pedals and all the other controls without looking at them. Touch-typing or playing any musical instrument requires you to move without looking at your hands. Even holding an object – a pen, a cup, a spoon, your partner’s hand – uses proprioception as well as the sensation of touch. Walking requires accurately moving hips, legs and feet and without proprioception becomes impossible without monitoring those limbs with your eyes, sending a continuous stream of corrections on the basis of what you can see, rather than the much faster and more accurate basis of what you “know”. The consequences for dancing should by now be obvious!
Nerve or neuron damage
Damage to proprioception can occur anywhere from the nerve sight where the “sensing” occurs through to the regions of the brain where proprioception is received and interpreted, and can occur through any form of nerve damage: Viral infections, Multiple Sclerosis, absence of blood, absence of oxygen in the blood, physical damage through puncturing, cutting, twisting or hyper-extension, poisons, and the list goes on.
When impaired proprioception is due to nerve damage and not a short-term problem such as alcohol poisoning or short-term restriction of blood to the muscles and nerves, treatment is necessarily limited to preventing further damage, microsurgery to resplice nerves if possible and physiotherapy in the hopes of stimulating nerve or muscle repair.
Compensatory strategies
Where treatment can not be total, the individual with impaired proprioception must learn management strategies. Looking at your limbs is one of the most fundamental strategies employed. Where voice is impaired, feedback can be obtained through the ears, or even by pressing your fingers against your throat while speaking, providing the sense of touch is intact. If you can not judge how tightly you are holding something (or someone), try looking for the skin to change colour with increased pressure.
Environmental modifications
Environmental modifications may also be necessary, such as clearing pathways through the home, changing cupboards and shelves so that you can also see the contents, keeping torches in useful locations, adding more light fixtures and sleeping with a night light that is sufficiently powerful to allow the eyes to compensate if you need to go to the toilet in the middle of the night.
Exercises
Most of the compensatory strategies do of course require training, and the best way to do that is to challenge what you can do and then increase the challenge. Standing on a wobble board can improve the use of vision to maintain balance. Juggling can improve the relationship between the hands and the eyes, as well as improving spatio sensory abilities. Tai Chi or Yoga are good for strengthening remaining proprioception and promoting alternatives, and any training or diet that improves visual acuity or your capacity to use your peripheral vision will of course aid any use of the eyes.
Professional assistance
If you have impaired proprioception and have not yet been given adequate assistance, the best people to speak to are neurologists, physiotherapists and occupational therapists. Speak to your hospital or your GP about a referral.
References:
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Proprioception 
Proprioception