Testing for Lameness

Why is testing for lameness important?

Lameness is a sign of discomfort or pain in a pet. Understanding the cause of lameness can help you and your veterinarian develop the best plan for reducing or eliminating that pain and improving your pet’s ability to move comfortably.

What might be causing my pet’s lameness?

The most common cause of lameness is trauma or injury to joints, ligaments, tendons, muscles, or bones. Other causes of lameness include developmental diseases in young animals, degenerative joint disease in older pets, immune-mediated joint disease, infectious joint diseases, neurological disorders, and cancer of the bones or joints.

How is the cause of a pet’s lameness determined?

Finding the cause of a pet’s lameness usually starts with a complete history and physical examination.

Your pet’s history includes details such as:

• Whether the lameness occurred suddenly or came on gradually
• Whether trauma was involved
• Whether more than one limb is affected
• Whether the lameness is constant or comes and goes
• Whether there are other signs of illness

The physical examination starts with assessment of your pet’s overall health and is followed by a lameness exam, which includes:

• Evaluation of how your pet walks and stands
• Palpation (feeling) of their back and affected limb(s)
• Assessment of joint motion

Your veterinarian is looking for evidence of trauma such as bruising or wounds, and signs of soreness such as swelling, heat, redness, pain, or abnormal movement within a joint or leg.

Specific tests can suggest a specific condition. For example, if the cruciate ligament in the knee is damaged, there will be abnormal movement when the veterinarian tests the joint in a particular way, called a drawer test or tibial thrust. The drawer test is more reliable when the pet is completely relaxed, so the test is often done while your pet is sedated. If this test finds abnormal movement, it is referred to as a drawer sign.

What diagnostic tests are commonly done in a pet with lameness?

If your pet has additional signs of illness, such as fever, poor appetite, lethargy, or weight loss, then underlying systemic illness may be present and screening tests may be recommended, like a complete blood count (CBC), a serum biochemistry profile, and a urinalysis.

If a pet appears to be healthy except for lameness, imaging tests are often recommended:

• X-rays (radiographs) are often recommended to check the bones for abnormalities. Sometimes, changes in the joint or soft tissue (muscle, tendons, and ligaments) can be seen on X-rays but often, alternative ways of imaging these tissues are needed.
• Ultrasound uses sound waves to provide images of joints and soft tissues like muscle, tendon, and ligament. It can help detect and measure soft tissue strains or tears as well as certain types of joint disease.
• CT and MRI provide highly detailed images that allow for more thorough assessment of your pet’s bones and soft tissues than X-rays. By providing cross sectional images, they give your veterinarian more of a three-dimensional picture of the problem area, which allows for a more targeted treatment plan.

If your pet’s joints appear swollen, your veterinarian may recommend obtaining a sample of joint fluid (also called synovial fluid) for testing. This analysis includes looking for signs of infection (bacterial culture), as well as evaluating the type of cells present that could be caused by inflammation, immune-mediated disease, or a tumor.

What other diagnostic tests might be done?

Depending on the results of the history, physical exam, and screening tests, specific blood tests may be recommended to diagnose infectious diseases that cause lameness (e.g., Lyme disease, ehrlichiosis, or fungal infection). There are also specific antibody tests that can help to confirm a diagnosis of immune-mediated joint disease, such as the rheumatoid factor test.

If X-rays reveal a mass or an area of abnormal-looking bone, then fine needle aspiration or surgical biopsy of the area may be recommended to determine if there is inflammation, infection, or cancer.