The kitchen knife is the better of the two types of knives in project zomboid. Although it is fairly common, it is still a decent weapon if you are unarmed.
In combat, the kitchen knife takes 2-4 strikes to kill, similar to the baseball bat. However, the kitchen knife has a smaller range and much less knockback. Although it is a decent weapon, replacing it would be a good idea as a kitchen knife is not suitable for fighting 5+ zombies at once. Its range is somewhat longer than the hammer, so if you miss, don't miss again.