Unexplained Inflammation
of Cat's Leg

by Greta
(Bronx, NY)

My 10-year-old indoor cat has been limping for the past week. I brought him to the vet, and the vet sedated him for a full exam, finding no wounds or bruising, but severe inflammation of the muscle in the back right leg. She noted that this presentation is quite unusual and she has never seen a case like this. Specifically, the X-ray revealed nothing abnormal in the bone. A needle aspiration from the muscle was inconclusive b/c she wasn't able to get a sample. She has put him on a steroidal anti-inflammatory temporarily and suggested we monitor him. If he doesn't improve, she suggested a referral to an orthopedist and a muscle biopsy to rule out cancer. Poor Gonzo (our cat) is in pain, and I want to be sure I'm taking the right course of action. Any thoughts about what it could be? or things we should keep in mind in making an appropriate action plan for him.


Hi, Greta,

I am so sorry about Gonzo's discomfort and your worry. I certainly understand how you feel. It's so hard to watch our beloved pets suffer.

The action that has been taken thus far has been quite appropriate. In fact, I would have followed the same course of action exactly. Indoor cats that are suddenly limping have usually jumped or landed wrong and are temporarily lame because they have "pulled a muscle". Radiographing the leg (x-ray)to rule out a fracture or other change in the bone is appropriate. If nothing is found, a course of steroidal anti-inflammatory medication is prescribed and most often brings the matter to an end.

Fine needle aspirates are great when they yield a result and very frustrating when they don't. They're worth doing since it's a minor procedure, and are wonderful when they provide a diagnosis. Approximately 50% of the time, however, the procedure is not diagnostic, through no fault of the veterinarian.

When you report that she found severe inflammation of the muscle, I am assuming that what she felt was a uniformly swollen, slightly enlarged muscle, not a discrete mass that was part of the muscle. If that is correct, then waiting to see if the condition improves from time and the medication is the right course of action. If, however, she felt a "lump" in the muscle, the referral to the specialist should be right away.

The possibilities are fairly limited as to the cause. Trauma, as I mentioned before would be at the head of my list. However, cancer would have to be on the list also. Again, if the muscle was uniformly swollen and not a smaller, discrete mass in it, inflammation from trauma would be by far the most likely cause.

You might want to try and remember if vaccines were ever given in that leg. While rare, there have been occurences of fibrosarcomas at the site of a vaccine. It can occur soon after the injection or many years later. Again, that would almost always present itself as a "lump".

However, if you know absolutely that a vaccine was given in that very location, I would probably schedule an appointment with the surgeon if the condition is not greatly improved within the next week.

I don't mean to worry you. I know you want to cover all bases and certainly, the earlier anything is diagnosed, the better the prognosis. However, I want to remind you that I have seen many, many cats who are lame from trauma and very, very few who have developed a fibrosarcoma.

Thank you for writing and for being such a loving "mommy" to Gonzo. He's a lucky cat to have such a caring and concerned owner as yourself.

Dr. Neely