Your pet has developed a limp. What do you do? It is easiest to think about this process the same way you would if it happened to you.
Most injuries that cause limping in animals are similar to sprains or strains in people. These are called soft tissue injuries in veterinary lingo. They get these the same way we do -- overexertion, landing wrong on a leg when jumping, cutting too sharply on a planted limb. So how do you know the difference between these types of injuries or more serious ones, such as fractures or back injuries? Follow some simple guidelines and you can save yourself the worry and money of immediate x-rays.
Evaluate exactly what your pet is doing. If the limp developed suddenly and is intermittent, wait and watch. Don't let your pet run or jump and minimize its activity. If the limp seems to ease over the course of several days, problem solved. If not, a vet visit may be necessary.
Some limps are severe. If your pet is exceptionally painful, non-weight bearing, or there is obvious swelling or deformity involving the limb, a trip to the vet is indicated. If you take your pet to the vet, don't be afraid to discuss all options available for your pet's treatment. If no fractures, ligament tears, or abscesses (common in cats) are detected on physical examination, ask your vet if it is possible to prescribe pain meds and forced rest prior to anything more invasive or dramatic.
If you decide to wait and watch, there is one thing to remember. DO NOT GIVE YOUR PET ANY PAIN MEDICATION FROM YOUR MEDICINE CABINET without first consulting with your veterinarian. Aspirin, Tylenol, and products like these can do more harm than good for your dog if given incorrectly. In cats, they can be deadly.
If you have an older pet or a pet with any sort of preexisting illness, limping can be symptomatic of much more serious issues. Likewise, dogs with histories of back injuries and specific breeds of dogs (like dachshunds) that are prone to back injuries need to be watched a bit more closely. If your pet ever has acute onset of pain or difficulty moving its back end, be careful!! Back injuries may require immediate medical attention. Most injuries of that nature cause problems with both back legs, so if your pet is focused on one leg only, it is less likely to be a back issue.
Neck injuries can manifest themselves as lameness in either front or hind legs as well. If your pet is holding its head in a strange posture, or seems to be painful when the neck is touched or manipulated, see your veterinarian right away.
The bottom line here is simple: Your pet will respond proportionally to its injury. A slight favoring of one leg or foot, where the pet sometimes puts weight on the injured appendage, is a very different injury from one that causes severe pain and completely non-weight bearing movement. By paying attention to exactly what your pet is doing, you can respond accordingly.