Joint Effusion (Swelling)
Diagnosis In-depth A radiograph of the affected joint may reveal a fracture, tumor, degenerative joint disease or erosive bony destruction. Distention of the joint can often be visualized. Most of the time, sedation is required for taking x-rays of joints, as they are difficult to position and are usually painful. Radiographs are a very useful tool for evaluating joint effusion.
A complete history and physical exam is vital in the evaluation of an animal with joint effusion. A history of trauma or current illness should be noted. Some causes of joint effusion are more common in certain geographic locations (tick borne diseases), so a travel history should be recorded. Determining if single or multiple joints are affected is an important part of the physical exam. Additional tests include:
Arthrocentesis, or the sampling of joint fluid, is an excellent way of determining the cause of the effusion. Effusions caused by trauma, infectious diseases, immune disorders or degenerative conditions all have characteristic cytology (a microscopic evaluation of cell types). White blood cells, red blood cells, and even occasional organisms can be identified. The numbers of white blood cells are counted, and the types of white cells (specifically: neutrophils, lymphocytes, monocytes, macrophages, and eosinophils) are proportionately recorded.
If polyarthritis (more than one joint affected) is suspected, multiple joints can be sampled to confirm the diagnosis. The joint fluid is also cultured to check for any bacterial agent that might be responsibly for the effusion. The cytology of the joint fluid can often give a definite diagnosis alone, but other times the results need to be interpreted considering additional diagnostics.
A CBC is an important test to include when infection or polyarthritis is suspected. With an infection, the white cells might be elevated. Platelets are blood cells that help with clotting, and their numbers are typically estimated or counted on a CBC. Low platelet counts (thrombocytopenia) could cause hemarthrosis or be related to other causes of polyarthritis. Since polyarthritis is a systemic disease, the red cell count should be checked for anemia and a white cell count evaluated. Both tick borne and immune mediated diseases are systemic illnesses that often have changes in red and white blood cell counts.
A biochemical profile is important in evaluating liver and kidney status. Many causes of polyarthritis, specifically immune and infectious, can be associated with liver or kidney disease.
A urinalysis is needed to evaluate kidney function. Occasionally, protein loss through the urine may occur due to various immune diseases or infectious agents. Protein loss may be quantified by a urine protein creatinine ratio. The amount of protein loss may correlate with specific diseases.
Chest and abdominal radiographs are sometimes needed if there is a concern of cancer, immune or infectious diseases.
Infectious disease titers may be drawn to test for Lyme disease, ehrlichia, and Rocky Mountain spotted fever. If an animal has been vaccinated for Lyme disease, a western blot should be done to separate a vaccine-induced titer from true infection.
Immune panels to include a rheumatoid factor and an ANA may be done if immune mediated polyarthritis is suspected. These tests should be interpreted with caution, as false positives and false negatives are common findings.
CT or MRI scans may be done in cases of single joint effusion where a subtle lesion is suspected as having caused the joint effusion. These tests are usually done at referral or specialty clinics.
Synovial or bone biopsies may be done if a tumor of the joint capsule or bone is present. Definitive diagnosis can only be made through a biopsy.
One or more of the diagnostic tests described above may be recommended by your veterinarian. In the meantime, treatment of the symptoms might be needed, especially if the problem is severe. The following nonspecific (symptomatic) treatments may be applicable to some, but not all pets with joint effusion. These treatments may reduce severity of symptoms or provide relief for your pet. However, nonspecific therapy is not a substitute for treatment of the underlying disease responsible for your pet's condition.
Pain relief may need to be provided. No medication should be given without first speaking to your veterinarian. Some medications that are often used for pain relief include non-steroidal anti-inflammatory drugs and narcotics. Controlling the pain is important in making your pet comfortable until veterinary care can be obtained.
If trauma or a fracture is suspected a bandage may be applied. Decreasing the range of motion in the joint and providing support may make your pet more comfortable and less painful.
Occasionally joint effusion is associated with more severe systemic illness and intravenous fluid support may be needed to stabilize your pet pending test results. Fluid therapy prevents dehydration and may be needed if an animal is in shock.
Once appropriate diagnostic tests have been submitted and infectious disease is suspected, antibiotics might be started. Starting antibiotics prior to getting the appropriate samples may prevent accurate diagnosis. Once tests are pending, starting antibiotics might be appropriate.