Doctors check for arthritis using a combination of physical examination, blood tests, imaging, and sometimes fluid drawn directly from the joint. No single test confirms every type of arthritis, so the process typically involves layering several of these together to identify which type you have and how far it has progressed.
What Happens During the Physical Exam
The exam starts with your doctor looking at and touching the joints that are bothering you. They’ll note any redness, swelling, warmth, or visible deformity, and they’ll compare each affected joint to the same joint on your opposite side (or to their own, as a baseline). This side-by-side comparison makes subtle swelling or shape changes easier to spot.
Next comes range of motion testing. Your doctor will first ask you to move the joint yourself, which reveals how much pain, stiffness, or weakness you’re dealing with. Then they’ll move the joint for you. If range of motion is still limited when someone else is doing the moving, that points to a mechanical problem like scarring, swelling, or bone changes rather than just pain or muscle weakness.
Your doctor will also feel for crepitus, a grinding or crackling sensation (sometimes audible) that happens when damaged joint surfaces move against each other. It’s caused by roughened cartilage or irritated tendons, and the specific motion that triggers it helps narrow down which structure is involved. They’ll also try to distinguish between different types of swelling by pressing on the joint. Fluid buildup inside the joint feels different from thickened tissue lining, which feels different from bony enlargement caused by bone spurs.
Questions Your Doctor Will Ask
Before or during the exam, your doctor gathers a detailed history. The pattern of your symptoms matters as much as the symptoms themselves. Expect questions about when the pain started, whether it came on gradually over months or ramped up over a few weeks, which joints are affected, and whether the problem is symmetrical (both knees, both hands) or one-sided.
Morning stiffness is one of the most telling clues. Osteoarthritis typically causes mild stiffness that loosens up within a few minutes of moving around. Rheumatoid arthritis causes stiffness that lasts an hour or longer and is sometimes the very first symptom people notice. Your doctor will also ask about fatigue, fever, or general weakness, since rheumatoid arthritis often starts with flu-like symptoms before significant joint pain appears.
Blood Tests That Help Narrow the Diagnosis
Blood work is especially important when inflammatory arthritis (like rheumatoid arthritis) is suspected. Two key antibody tests are typically ordered together:
- Rheumatoid factor (RF) is an antibody found in the blood of many people with rheumatoid arthritis. It’s not definitive on its own, though. Some people with RA never test positive, and some people who test positive never develop the disease.
- Anti-CCP antibodies are more specific to rheumatoid arthritis and can appear in the blood before symptoms even start, making them useful for early diagnosis. Combined with RF results, they give doctors much stronger confidence in confirming RA.
Two additional blood tests measure inflammation levels in your body. The erythrocyte sedimentation rate (sed rate) and C-reactive protein (CRP) test both rise when inflammation is active. Elevated levels don’t tell your doctor which type of arthritis you have, but they confirm that an inflammatory process is happening and help track whether treatment is working later on.
Osteoarthritis, by contrast, is not an autoimmune condition. It’s caused by cartilage wearing down over time. Blood tests are often normal in osteoarthritis, which is itself a useful diagnostic clue. If your symptoms suggest arthritis but your inflammatory markers and antibodies come back clean, osteoarthritis becomes more likely.
What Imaging Can Reveal
X-rays are usually the first imaging study ordered. They show the hallmarks of osteoarthritis clearly: narrowing of the space between bones where cartilage has worn away, bone spurs forming along joint edges, increased bone density underneath the lost cartilage, and sometimes fluid-filled cysts within the bone itself. X-rays can also reveal joint damage from rheumatoid arthritis, though the changes may not appear until the disease is more advanced.
MRI is far more sensitive. It can detect subtle cartilage degeneration, fluid buildup in the bone marrow, and soft tissue inflammation that X-rays miss entirely. This makes MRI particularly valuable for catching arthritis in its early stages or for evaluating damage to ligaments and other soft tissues around the joint.
Ultrasound fills a different niche. It’s excellent at identifying fluid-filled cysts that form in arthritic joints and at evaluating the ligaments and tendons surrounding a joint. It’s also used in real time to guide a needle directly into a joint when your doctor needs to draw fluid for analysis, since the radiologist can see the needle, the joint space, and nearby blood vessels on the screen simultaneously.
Joint Fluid Analysis
Sometimes the most definitive answer comes from examining fluid drawn directly from a swollen joint. This procedure, called aspiration or arthrocentesis, involves inserting a needle into the joint space and withdrawing a sample of synovial fluid.
This test is especially critical for diagnosing crystal-related arthritis, including gout and calcium pyrophosphate arthritis. In many cases, these conditions cannot be diagnosed with certainty any other way. The fluid is examined under a microscope for the presence of specific crystals, and the type of crystal identifies which condition is causing the inflammation. Joint fluid analysis can also help rule out infection, which can mimic arthritis symptoms but requires completely different treatment.
How Doctors Tell Osteoarthritis From Rheumatoid Arthritis
The distinction between these two common types of arthritis runs through nearly every step of the diagnostic process. Osteoarthritis develops gradually over months or years as cartilage breaks down. It tends to affect weight-bearing joints and the joints closest to your fingertips. Pain worsens with activity and improves with rest.
Rheumatoid arthritis is an immune system disorder that progresses over weeks to months. It favors the hands, wrists, and feet, usually in a symmetrical pattern (both sides of the body at once), but it typically spares the joint closest to the fingertip. Morning stiffness lasting well over an hour, elevated inflammatory blood markers, and positive antibody tests all point toward RA. Osteoarthritis patients typically have normal blood work and shorter morning stiffness.
Which joints are involved, how many, and whether the pattern is symmetrical also matters. Symmetrical involvement of many small joints suggests rheumatoid arthritis. One or a few joints affected asymmetrically is more consistent with osteoarthritis or psoriatic arthritis. Larger joints and the spine point toward a group of conditions called spondyloarthropathies.
What to Bring to Your Appointment
You can make the diagnostic process faster and more accurate by tracking your symptoms before your visit. Note which joints hurt, when the pain is worst, how long morning stiffness lasts, and whether you’ve noticed swelling, redness, or warmth. Write down any family history of arthritis or autoimmune conditions. If you’ve had previous X-rays or blood work done elsewhere, bring those records or have them sent ahead. The more information your doctor has from the start, the fewer repeat tests you’ll need and the sooner you’ll have an answer.