A dog that has sprained it's leg will usually show signs of the sprained leg in the dog such as limping, swelling, pain, swelling in the joints and even swollen paws.
Your dog may also have a loss of appetite, red and inflamed joints, compulsive licking of the area where the sprain is, aggression that happens suddenly or aggression that is unexplained.
Your dog may also lose interest in playing or doing other activities that it would normally be interested in.
If the dog has sprained it's leg then the dogs sprained leg should heal and recover within a few days to a week and usually no vet visit or medical treatment will be needed.
However if the sprained leg is not healing or the dog is in more pain then taking the dog to the vet would be a good idea.
You can apply an ice pack to the dogs sprained leg and let it rest for awhile with the ice pack which can help with the sprained leg.
You can also give the dog some pain medicine such as aspirin that us humans take and it's safe for dogs as well.