The joints in a horse’s limbs are filled with a thick, smooth, clear fluid that lubricates the joint and allows it to move easily and smoothly. When the capsule holding this fluid gets damaged, it can allow bacteria and inflammatory cells to enter the joint. This causes noticeable swelling and heat emanating from the joint, as well as lameness. Without treatment, this can quickly progress to a serious injury.
A joint fluid tap can be performed in the hospital, where a needle is inserted into the joint and a small sample of the fluid is extracted. A cell count is performed in the lab, which gives an indication of the level of infection/inflammation. The total amount of protein in the fluid is also measured –normal healthy joint fluid has a low total protein level, so a higher level can indicate problems. Finally, a smear of the joint fluid can be carried out, which will determine whether a high cell count is due to inflammation or other unrelated issues. Once diagnosed, the hospital staff can begin to treat the horse’s problems effectively.
Not all abnormal joint fluid samples will be due to a present infection. Osteoarthritis is common in horses, and can lead to chronic lameness and discomfort. There are many treatments available for osteoarthritis, including the new IRAP procedure. Talk to your vet if you have any questions regarding the disease or its treatment options.
Peritoneal tap samples are extremely useful in diagnostic situations, particularly within the hospital where emergency admissions are frequently seen. Taken using a needle through the skin and abdominal wall, they are most commonly used in the diagnosis and management of colic and peritonitis, although the fluids are also useful when injury to the abdomen or internal organs is suspected.