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CELLS IN SYNOVIAL FLUID First broadcast on www.provet.co.uk Focus on Orthopedics Week. |
This information is provided by Provet for educational purposes only.
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.
Several different types of cell mat be seen in synovial fluid aspirates
The cell count in normal synovial fluid can vary greatly from joint to joint in the same individual. It is generally accepted that the normal range is an average of 0 to 3000 cells/ml. On average you should expect to see about 2 cells/field at 400x magnification in normal synovial fluid.
| Cell Type | Comments |
| Lymphocytes | The most common cell type (up to 100% of nucleated cells has been reported) found in normal synovial fluid samples. Both B and T lymphocytes are found. |
| Monocytes | Are found in normal synovial fluid samples |
| Neutrophils | Are found in normal synovial fluid samples. Should be <12% of nucleated cells. Often <5%. |
| Macrophages | Rare in synovial fluid samples. Reactive macrophages look similar to synovial membrane cells type A and type B. |
| Eosinophils | Abnormal finding |
| Synovial membrane cells (clasmatocytes) | Are found in normal synovial fluid samples |
| Red blood cells | Rare. Most likely due to contamination during the collection process. Also due to haemorrhage. |
| Chondrocytes | Abnormal finding |
| Osteoblasts | Abnormal finding |
| Osteoclasts | Abnormal finding |
| Lupus erythematosus cells | Abnormal finding |
| Microorganisms | Abnormal finding |
| Tumour cells | Rare but highly significant |
The number of large mononuclear cells (monocytes, macrophages or clasmatocytes) that are vacuolated or and contain phagocytosed cells, debris, microroganisms should be counted because they are significant.
Abnormal cell appearances should also be recorded including :
- Karyolysis - dissolution of cells- suggests infection
- Karyhorrhexis - cells break up into fragments
- Pyknosis - cell nuclei shrink and become densely basophilic
Inflammatory diseases and infectious diseases cause an increase in white cells, aparticularly mononuclear cells.
Last updated : January 2016