diagnosing arthritis

Your vet will likely offer a blood test during the diagnosis of arthritis. This is an essential component of a good management plan for a number of reasons.

1. Arthritis is most prevalent in older dogs who are more prone to other chronic conditions that can also cause lethargy and weakness. Having a blood test to rule out other possible diseases is crucial for an accurate diagnosis. A blood test may highlight other chronic conditions which will affect the way your dog responds to the medication prescribed. For example, a dog with liver disease may not process the pain relief drugs as well as we would expect, putting them at increased risk of toxicity.
2. The blood test provides a baseline to refer back to during the treatment in case of complications.
3. On finding a second condition, or possibly a third, an owner may question whether further management is right for their dog.

Urine tests are a simple and non-invasive test which can be very helpful in picking up acute or chronic conditions that need to be taken into account when treating your dog’s arthritis. They may be used during diagnosis and monitoring of the disease. 

It is worth bearing in mind that they are much less sensitive at picking up important changes in your dog’s organ function than a blood test, so are not appropriate for long term monitoring on their own in most cases.

As osteoarthritis progresses, there are lots of changes in the affected joint. The articular cartilage erodes, bone below that cartilage hardens and becomes exposed, the protective joint capsule becomes inflamed and thickened, and small growths of bone (osteophytes) form around the joint.

Recognising osteophyte formation on a radiograph is a clear indicator of arthritic change in that joint. These changes may be seen in one or more joints. Knowing which joints are affected by arthritis will allow treatments, particularly rehabilitation therapies, to be targeted at problem areas. 

Radiographs can also help to rule out other conditions that can mimic the signs of arthritis, such as fractures, dislocations, bone tumours, or bone infections. An accurate diagnosis is really important in order to ensure correct treatment.

Your dog will need to be sedated or have a general anaesthetic to allow your vet to get a good, diagnostic set of radiographic images. Attempting to take radiographs without sedation can cause distress and discomfort to your dog,  as well as resulting in poor quality uninterpretable images. For radiography to be useful, the dog must be perfectly still during the procedure.

There are some limitations to interpreting radiographs, as changes in the bone may not be seen until late on in the process of arthritis, when a lot of damage has already been done to the joint. This means mild or early cases of arthritis could be missed, even though the joint disease is still present and the dog is still experiencing pain. 

Equally, a joint with a lot of boney changes on radiographs may be well controlled and not causing the dog pain, despite how it appears. For this reason radiographs need to be carried out in conjunction with a good physical examination by a vet, and good observations by the owner.

A CT scan is almost like a 3D radiograph - it is particularly helpful for looking at areas that are difficult to assess on a standard radiograph e.g. the elbow joint. It is likely your dog would need to be referred to a specialist hospital to have this type of diagnostic scan, as it is not available in most first opinion general practices.

Arthrocentesis (Joint tapping)

Osteoarthritis is the most common form of arthritis in dogs. However other forms of arthritis also exist, and if your vet is concerned about one of these other types of arthritis they are likely to want samples of your dog’s joint fluid to do a further assessment.

Your dog will need to be sedated or given a general anaesthetic to allow for this test to be carried out. A sterile needle will be inserted into the joint, in order for a sample of the fluid to  be removed and examined for signs of inflammation or infection.