You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

Examination of synovial fluid is a useful test to aid in the differential diagnosis of joint disease.

Apart from acute or chronic trauma several orthopaedic diseases lead to:

• Changes in the biomechanical forces acting within a joint, or 
• Changes in nutrition of the structures within the joint

and these can lead to degenerative joint disease. Diseases which can cause degenerative joint disease (DJD) include :

• Elbow dysplasia
• Hip Dysplasia
• Legg Perthe Calves Disease (avascular necrosis of the hip)
• Ligament injuries eg rupture of the cruciate ligament
• Osteochondritis dissecans
• Osteoarthritis 
• Patella luxation

In other cases the cause is unknown (idiopathic).

Cytological examination of synovial fluid from cases with DJD usually produces the following results :

 

Test	Findings
Volume of synovial fluid	Slight to marked increase
Colour	Normal
Turbidity	Normal
Viscosity	Normal. Occasionally slightly decreased.
Mucin Clot Test	Normal. Occasionally poor.
Total protein	Normal. Occasionally slightly increased.
Synovial fluid clots when left ?	No
Total red cells	Normal or slight increase. Increased during periods of increased inflammation.
Total nucleated cells	Normal. Occasionally slight increase.
% mononuclear cells	Normal. Occasionally slight increase. If increased in numbers they have increased phagocytic activity (seen as vacuolated cells)
% neutrophils	Normal. Occasionally absent or slight increase.
Abnormal cells - chondrocytes, osteoclasts	Rare. Only if damage to articular cartilage is severe (seen in horses).

One advantage of performing cytology is that subtle changes may be detected before there is radiographic evidence of disease.

Last updated : October 2013