It takes little body sway to the outside before one starts falling to the outside. Either the ankle rolls outward or a quick counter active step is required by the other foot to stop the fall, along with arm movements and body leans. After a few episodes of this, the body makes further compensations. The individual starts walking with the legs wider apart and decreased speed to regain stability and security. This strategy is taxing on the body, energy, endurance, and metabolic rate.
Muscles work together in balance.
They work like a pulley system. Imagine a rope looped around a pulley, with equal lengths. If there is an equal pull on each side the pulley will not move. If the pulley is pulled on only one side, then the pulley rotates to that side. Muscles work on the body in a similar fashion.