We need balance to protect our body from a fall injury. From physics we learned about dynamic and static balance. Dynamic balance can describe our body in motion when we walk or run. Static balance is when we stand still or are sitting without back support. Generally, you are in balance if you are not falling voluntarily.
Poor eyesight or other eye related health issues can lead to poor balance. Low blood pressure can cause dizziness and cause falls from poor balance. Many balance disorders can begin all of a sudden and with no obvious cause.

vestibular system image

A balance issue can make you feel unsteady or dizzy, as if you are moving, spinning, even though you are not moving at all. Some health conditions, inner ear issues, medications or many brain disorders can cause balance problems. Our sense of balance is primarily controlled by a structure in our inner ear called the labyrinth. At one end of the labyrinth is a system of loops and pouches called the semicircular canals and the otolith organs. These help us maintain our balance. The complete organs in the inner ear which control our balance is named Vestibular System.
A balance disorder may be caused by infections in the ear, a head injury, or blood circulation disorders that affect the inner ear or brain. As we get older it is not unusual to begin to experience problems with our sense of balance. This is most often due to a natural decrease in eye sight, hearing, and loss of muscle strength. Other factors that can cause difficulty with balance are problems with visual and skeletal systems, and the nervous and circulatory systems. Problems in the skeletal system such as arthritis also may cause balance problems.
As we get older there is an increased tendency to reduce physical activity which leads to an overall decrease in muscle strength. Our posture is very much dependent on muscle strength to secure a good body position in standing or sitting positions. Weak skeletal muscles would not be able to work with our vestibular system to insure good balance.