Infection alert

Infection of synovial fluid can present a threat to life, but the prognosis is usually good with prompt care. Therese de Souza MRCVS explains

SYNOVIAL sepsis is when there is infection or contamination within a structure that contains synovial (joint) fluid.

The structures that can be involved include (see box, right):

• Joints
• Tendon sheaths - sleeves of fluid through which tendons run
• Bursa a sac of fluid that contains synovial fluid, normally over a bony prominence.
• It is recognised as a frequent cause of injury, disease and, sadly, death in horses.

HOW DOES IT OCCUR?

IN the adult horse, synovial sepsis usually results from a direct penetration of the synovial structure following a wound. Sometimes no wound is clearly visible, but the infection may have resulted from a penetration, such as in the case of blackthorn injuries. Often the wound can be very small, or not dramatic to look at, but it overlies an important structure.

Horses can also develop synovial sepsis after medication or surgery into a joint, tendon sheath or bursa but this is very rare, occurring in less than 1% of cases.

Foals can contract synovial sepsis due to similar causes as adult horses, but a case in foals would normally result from infection spread from the bloodstream. This is sometimes called "joint ill" and can be accompanied by other sources of infection in the foal, such as an umbilical infection or pneumonia.

THE SIGNS

THE signs of synovial sepsis vary, but normally involve a collection of the following:

A wound overlying a synovial structure

A swollen and painful synovial structure

Lameness – this can vary from mild to severe non weight-bearing lameness

Fluid leaking from a wound overlying a synovial structure