How Is Arthritis Diagnosed? What X-Rays, MRI and Ultrasound Can Show
Your knees ache when you climb stairs. Your fingers feel stiff in the morning. The pain has lasted for weeks, so your doctor has ordered imaging. Now you want to know what the test will show and whether it will finally explain what's going on.
Imaging is a key part of an arthritis diagnosis. Doctors use it to confirm the diagnosis, identify the type of arthritis and decide on treatment. This guide explains how arthritis is diagnosed, what each imaging test can and can't show, and how imaging helps track arthritis over time.
The Arthritis Diagnosis Process
How Is Arthritis Diagnosed?
No single test diagnoses arthritis. Doctors put together three kinds of information.
- Your history and symptoms. Your doctor asks which joints hurt, when the pain started and whether stiffness is worse in the morning or after activity.
- A physical exam. Your doctor checks each joint for swelling, warmth, tenderness and range of motion.
- Tests. Blood tests and imaging fill in what the exam can't show.
The pattern of symptoms often points toward a type. Osteoarthritis usually comes from wear on the cartilage over time. Rheumatoid arthritis and psoriatic arthritis are inflammatory conditions, where the immune system attacks the joints.
How Do Doctors Test for Arthritis?
Blood tests look for signs of inflammation. They also help confirm inflammatory types like rheumatoid arthritis. If your doctor suspects gout or an infection, they may draw fluid from the joint to test it.
Imaging shows the joint itself. It reveals cartilage loss, bone changes, inflammation and fluid. That helps your doctor confirm the diagnosis and see how far the condition has progressed. The test your doctor orders depends on the joint and the type of arthritis they suspect.
X-Rays for Arthritis
Can You See Arthritis on an X-Ray?
Yes. An X-ray is usually the first imaging test doctors order for joint pain. X-rays show the bones and how they meet at each joint. That makes them good at showing the bone changes arthritis leaves behind.
For knee arthritis, you may be asked to stand during the exam. Standing puts your weight on the joint, which shows how much space is left between the bones. Like most X-ray exams, it takes only a few minutes and doesn't hurt.
What Does Arthritis Look Like on an X-Ray?
A radiologist looks for three main signs of osteoarthritis.
- Joint space narrowing. Healthy cartilage cushions the ends of your bones. An X-ray shows the gap that cartilage fills between the bones. When cartilage wears down, that gap gets smaller.
- Bone spurs. These are small bony growths, also called osteophytes, along the edges of the joint.
- Changes in the bone under the cartilage. The bone can become denser, and small cysts can form.
A normal knee X-ray shows an even gap between the thigh bone and the shin bone. A knee X-ray with osteoarthritis often shows a narrower gap, with bone spurs at the edges. Radiologists grade these changes as mild, moderate or severe. Your doctor uses that grade to help choose treatment.
Do X-Rays Show Rheumatoid Arthritis?
X-rays can show rheumatoid arthritis once it has damaged the joint. The main signs are erosions, which are small areas of bone loss near the joint. In early rheumatoid arthritis, though, the X-ray may look normal. Erosions may not appear on X-ray until up to two years after symptoms start. That's why doctors often add ultrasound or MRI when they suspect early inflammatory arthritis.
What Can an X-Ray Miss?
X-rays don't show cartilage, tendons, ligaments or inflammation directly. Early arthritis can cause pain before bone changes are visible. That's why some patients need more imaging after a normal X-ray. If your joint still hurts, your doctor may order an MRI or ultrasound next.
MRI for Arthritis
Does an MRI Show Arthritis?
Yes. An MRI scan shows both the bones and the soft tissue around them. It can show cartilage, ligaments, tendons and fluid that an X-ray can't. MRI is especially useful early on, since symptoms can start before damage is visible on a standard X-ray.
For rheumatoid arthritis, MRI is one of the most sensitive tests available. It can detect early erosions up to three years before they show up on an X-ray.
What Does Arthritis Look Like on an MRI?
A radiologist reviewing an MRI for arthritis looks for several changes.
- Thinning or damaged cartilage on the ends of the bones
- Bone marrow edema, which is fluid inside the bone near the joint
- Inflammation of the joint lining, called synovitis
- Extra fluid in the joint
- Tears or wear in nearby ligaments and tendons
These findings help your doctor tell arthritis apart from other causes of joint pain, such as a torn meniscus or a tendon injury.
Can an MRI Show Arthritis in the Lower Back?
Yes. Arthritis can affect the small facet joints that connect the vertebrae in your spine. An MRI can show wear in those joints. It can also show whether bone spurs or swelling are pressing on nearby nerves. Back pain has many possible causes, so your doctor will weigh the imaging options for back pain before choosing a test.
What If an MRI Makes You Claustrophobic?
Many people feel nervous about lying inside a closed MRI machine. An open MRI has more space around you and can feel more comfortable. Knowing how to prepare for your MRI ahead of time can also help you feel at ease.
Other Imaging Tests for Arthritis
How Does Ultrasound Help Diagnose Arthritis?
Ultrasound uses sound waves to create live images of the joint. It uses no radiation. It works best for joints close to the skin, like the hands, wrists, elbows, knees and ankles.
Ultrasound can show inflammation in the joint lining, fluid buildup and cysts. It's also excellent for checking the tendons and ligaments around a joint. In rheumatoid arthritis, ultrasound can spot inflammation and very small erosions that an X-ray may miss. Doctors also use ultrasound to guide a needle when they inject medicine into a joint.
When Do You Need an Arthrogram?
An arthrogram is a two-part exam. First, a contrast dye is injected into the joint. Then you have an X-ray, CT scan or MRI. The dye outlines the inside of the joint, so cartilage, ligaments and tendons show up in more detail.
Doctors usually order an arthrogram for pain that other scans haven't explained. It's most often used for the shoulder, wrist, hip, knee or ankle. Depending on the joint, your doctor may choose an MRI or CT arthrogram.
Does a DEXA Scan Show Arthritis?
No. A DEXA scan, also called a bone density test, measures how dense your bones are. It's used to diagnose osteoporosis and estimate your risk of fractures. It doesn't show joint damage, so it can't diagnose arthritis.
The two conditions are easy to mix up because their names sound alike. Osteoarthritis affects the cartilage in your joints. Osteoporosis weakens the bones themselves. You can have both, and your doctor may order a DEXA scan separately to check your bone health.
Which Scan Is Best for Detecting Arthritis?
The best scan depends on the joint, your symptoms and the type of arthritis your doctor suspects. Many patients start with an X-ray and add other tests if needed.
An X-ray is the usual first test because it shows joint space narrowing, bone spurs and erosions. If the X-ray looks normal but the pain continues, an MRI can show cartilage, soft tissue and early damage. MRI is also the most sensitive test for early rheumatoid arthritis.
Ultrasound works well for the hands, wrists and other joints close to the skin. CT gives a clear view of bone in deep joints like the spine and pelvis. An arthrogram is usually saved for pain that other scans haven't explained.
Using Imaging to Monitor Arthritis
Why Would You Need Follow-Up Imaging?
Arthritis changes over time, and imaging lets your doctor see those changes. A follow-up X-ray can be compared with your earlier images to show whether joint space has narrowed further. For this reason, X-rays are taken the same way each time.
For rheumatoid arthritis, follow-up imaging helps show whether treatment is controlling inflammation. MRI can also check for complications and show whether a treatment is working.
How Does Imaging Guide Treatment?
Your images help your doctor match treatment to the damage in your joint. Mild changes may call for exercise, physical therapy or medication. Ultrasound or CT can guide a needle for a joint injection. When arthritis is severe, imaging helps a surgeon decide whether joint replacement makes sense and plan the procedure.
Get Joint Imaging at Naugatuck Valley Radiology
Joint pain is easier to treat once you know its cause. Naugatuck Valley Radiology offers X-ray, MRI, ultrasound and arthrography for patients with joint pain and arthritis. Our 11 board-certified radiologists read every exam. NVRA was also the first ACR-accredited Diagnostic Imaging Center of Excellence in Connecticut.
We have locations in Waterbury, Prospect and Southbury. If you're paying out of pocket, see our self-pay pricing for imaging costs up front. Have a referral from your doctor? Contact us to schedule your exam.
