Page 384 - The Veterinary Care of the Horse

immediately when a wound penetrates a joint and thus can be confused with a fracture. If a

horse is lamer than expected with a tiny wound, the possibility of a joint infection should be
VetBooks.ir considered.

Infections resulting from joint injection are usually apparent within 2 days, but signs may be
delayed if the joint has been injected with corticosteroids or the horse is on non-steroidal

anti-inflammatory drugs such as phenylbutazone.
The diagnosis may be confirmed by the following.

SYNOVIAL FLUID EXAMINATION

• Normal synovial fluid is clear and a pale straw colour. If the joint is infected, it can be
cloudy, flocculent (contain debris) due to fibrin clots, darker yellow or orange in colour

and sometimes contains blood.
• Synovial fluid from an infected joint has a reduced viscosity.

• The white blood cell count is usually raised to above 30 × 10 /L with more than 90–95%
9
neutrophils.

• The protein level is raised to above 40g/L.
• Bacteria may be seen under the microscope.

• The fluid should be cultured to try and grow and identify the species of bacteria involved

and determine its sensitivity to different antibiotics.

RADIOGRAPHY

Radiographs are taken to determine the following.

• To rule out traumatic damage to bone.
• To assess whether there is any infection in the bones making up the joint; infection in the

bone is known as osteomyelitis or septic osteitis. If bone is infected it may show up as

areas of reduced bone density (lysis) or there may be an irregular pattern of new bone
production. The joint space may be widened or narrowed depending on the stage of the
disease.

SCINTIGRAPHY

Scintigraphy may be helpful in the early detection of bone infection but is rarely necessary.

ULTRASONOGRAPHY

Ultrasonography can be helpful for evaluating whether swelling is due to enlargement of the
joint or to thickening of the periarticular tissues. It may detect fibrin material within the joint