Q: Our guinea pig is less than 2 years old, and she has developed very swollen, painful hocks. She cannot use her back legs at all, and she squeals in pain if any pressure is applied to them. I took her to the veterinarian, and he gave her a prednisone injection and then oral prednisone to give her for a week. The week isn’t up yet, but I’m not seeing much improvement. She isn’t housed in a wire cage and she has a soft, dry cage floor. We have four other guinea pigs, and none of them have had any problems like this. I called another vet, who suspected scurvy, but all of my pigs get a 50 mg chewable vitamin C tablet daily in addition to their pellets, and she doesn’t have any other signs of scurvy. But the vet suggested getting a vitamin C liquid that is 500 mg per teaspoon and giving her a quarter teaspoon daily. I haven’t tried that yet. She is eating and drinking fine, but we have to bring the food and water to her because she can’t really get to it. Have you seen this in other guinea pigs? How is it treated? I don’t want to euthanize her, but if nothing can be done then I don’t want her to suffer.
A: I am sorry your guinea pig is so sick. When we hear of joint problems in guinea pigs, especially younger guinea pigs, we first think of vitamin C deficiency. Vitamin C is needed for the growth and repair of tissues in all parts of the body. Vitamin C is also necessary to make collagen, which is an important protein used to make cartilage, tendons and ligaments. Cartilage, tendons and ligaments are essential for the normal functioning of a joint like the knee, so when vitamin C is deficient, we see guinea pigs with problems using their knees.
A guinea pig needs a source of vitamin C every day because it is a water-soluble vitamin that is not stored in the body. And unlike almost all other animals, guinea pigs do not make their own vitamin C; they must ingest it in their food. Chewable tablets are an excellent method to make sure your guinea pig is getting enough Vitamin C each day.
For your guinea pig, if the collagen in the knees is diseased due to a deficiency of vitamin C, there should be an improvement within days of giving additional vitamin C. But if there is permanent damage due to long-term vitamin C deficiencies, additional vitamin C may not be able to repair extensive damage.
If there is just inflammation, the prednisone (an anti-inflammatory) might help in decreasing the swelling. Another possible explanation for what you described is infection, but that would be very unusual in both knees at the same time.
If rest and vitamin C do not seem to help your guinea pig, you may need to consider some diagnostic tests administered by your veterinarian. These would include radiographs of the knees.