The most important tools for diagnosing arthritis in dogs and cats (including osteoarthritis, or OA)are a detailed client history and a thorough physical examination by your veterinarian. It is helpful to know when clinical signs (symptoms) first developed, how quickly they progressed, and what factors appear to influence worsening or improvement of clinical signs. Based on history and physical examination, your veterinarian may recommend additional diagnostic tests. These tests can be important to rule out other problems that may cause similar signs, such as bone infection, fracture, luxation (dislocation), foreign material, cancer, or other problems.
Diagnosis of Arthritis in Dogs and Cats – Radiographs (X-rays)
Radiographs are helpful in diagnosing a cause for lameness and may also be advised if
your veterinarian suspects an orthopedic problem as the cause of nonspecific signs. Synovium and cartilage do not appear on radiographs, but bony changes, calcification of ligaments and tendons, and some inflammatory synovial fluid accumulation will. It is important to note that since the pain associated with OA results from soft tissue inflammation, the degree of bony change may not correlate to the degree of patient discomfort. For example, your pet may have severe pain without much bony change, or may seem almost normal with very abnormal radiographs. Bony changes develop in response to abnormal forces and are only a clue that underlying OA may be involved. Radiographs are very important to rule out problems listed above that may require surgery, antibiotics, or other therapy.
Diagnosis of Arthritis in Dogs and Cats – Joint Tap
Joint infections caused by tick-borne diseases or joint infection, such as from trauma, can cause lameness that may mimic OA. Depending on history, physical examination, and other tests, your veterinarian may recommend sampling synovial fluid as part of your pet’s diagnostic workup. This is especially important when joints are significantly swollen or signs occur suddenly. This is called a joint tap and requires sedation to perform properly. The fluid should be evaluated microscopically and in some cases sent to a laboratory to test for bacteria or other organisms. This is also an important test if your veterinarian suspects immune-mediated arthritis.
Diagnosis of Arthritis in Dogs and Cats – Bloodwork
Routine bloodwork should be performed on any geriatric pet (usually >8 years old for average dogs and >10 years old for average cats), and is very important if OA is suspected. This confirms appropriate immune function, rules out concurrent illnesses, and confirms that your pet is healthy enough to receive certain medications. Specific blood tests can be performed for numerous infectious diseases affecting joints.
Diagnosis of Arthritis in Dogs and Cats – Advanced Imaging
Advanced imaging, such as CT or MRI, can be extremely useful in diagnosing joint disease. These tests require anesthesia and can be very expensive, causing most owners to decline this option even when medically appropriate. The vast majority of OA patients are diagnosed and treated adequately without advanced imaging.
The following links provide more information about OA:
University of Illinois at Urbana-Champaign College of Veterinary Medicine