Stress fractures in a dog are caused when a dog puts too much pressure on a part of its body repeatedly. For example, Greyhounds sometimes get stress fractures on their legs because of the pressure on them when they run.
Limping is a sign your dog may have a stress fracture. If the dog's leg is hurt, the dog may favour the other legs and limp around, not putting any pressure on the hurt leg.
The area where there is a fracture may swell. This may be an indication your dog is injured. If the swelling is significant, it may be more than a stress fracture and you should take your dog to see a vet.
When a dog is hurt, it may be in shock and could go into depression. If you notice changes in your dog's behaviour such as depression, sleepiness and being uninterested in its usual activities, then it is possible the dog may have a stress fracture. The pain along with the inability to use the area that is fractured may culminate to create this mood swing.
If your dog is in pain and the area hurts when you touch it, then this may be an indication of a stress fracture. Depending on how bad the fracture is, the dog may snap at you if you get too close to the area. This makes it hard for you to inspect the wound, so if your dog is reacting like this, take it to a vet so it can get it looked at.