Missouri Revised Statute §273.036 imposes strict liability on a dog owner if the dog bites someone. This means that the owner could be liable to an injured party the first time the animal bites.
There are some significant limitations to this law, however. Firstly, the dog must have bitten the plaintiff, and an owner is not necessarily liable if a dog knocks someone over and injures them. An injured person can only hold the owner liable if the bite took place on public property, or private property if the plaintiff had permission to be there. A trespasser cannot seek damages for a bite that happened while they were on private property without permission.
An owner is also not liable if the plaintiff provoked the dog. A local dog bite lawyer could review the events around the incident to advise whether provocation might be a plausible defense that would defeat a claim for damages in a particular case.