When you fall on a sidewalk there are a number of potentially responsible parties. These responsible parties can be put into three major categories: Municipality, abutting landowner, and abutting business owner.
While the city generally has a primary responsibility to maintain sidewalks (different rules may apply to parking strips and planting strips) responsibility can also fall on the shoulders of abutting land and business owners. (Abutting in this context means owning property that runs up to the edge of the sidewalk (and in many instances beneath the sidewalk)).
Liability for all three groups can flow from both acts and omissions. For instance, an abutting landowner may be held liable if a tree on his or her property grows roots which cause a portion of the sidewalk to tip up (this condition is generally known as a “stub toe”). Similarly the city may be held liable for failure to either properly construct or maintain the sidewalk. Abutting business owners can be held liable for causing slippery substances – like oil – to make their way onto the sidewalk (this is often the case with service stations).
In certain situations it make sense to file suit against defendants falling into all three classes. In others, it makes sense to focus on only one (for instance, the city responsible for maintaining the sidewalk). In order to make the best decision about the potential defendants in the loss, it makes sense to consult with a personal injury attorney.