Bursitis is usually diagnosed through a physical exam, often without any imaging or lab work at all. A doctor presses on the area around the affected joint, checks your range of motion, and looks for the hallmark signs: localized tenderness, swelling, and pain with specific movements. When the cause is unclear or infection is a concern, fluid analysis, ultrasound, or MRI may follow.
What Happens During the Physical Exam
The physical exam is the foundation of a bursitis diagnosis. Your doctor will press directly on the bursa (the small fluid-filled sac cushioning the joint) to check for tenderness. In acute bursitis, this pressure typically reproduces your pain. They’ll also look at the overlying skin for redness, warmth, or signs of trauma, since these can signal infection.
Range of motion testing is a key part of the evaluation. You’ll be asked to move the joint yourself (active motion) and then your doctor will move it for you (passive motion). A pattern where active motion hurts but passive motion doesn’t strongly suggests bursitis, because your muscles and tendons are compressing the inflamed bursa when you move on your own. With some types, like bursitis at the kneecap or elbow, bending the joint reproduces pain but straightening it does not.
Chronic bursitis looks different. Because the bursa has had time to stretch and accommodate extra fluid, you may have significant swelling and thickening but little or no pain. The diagnosis in these cases leans more on visible swelling and the history of repetitive stress or prior flare-ups.
One important limitation: deep bursitis, like in the hip, may not produce any tenderness when the doctor presses on the area, and skin changes won’t be visible. That’s where specific physical tests and imaging become more important.
Physical Tests for Hip Bursitis
Hip bursitis (often called greater trochanteric pain syndrome) has its own set of hands-on tests because the bursa sits deep beneath muscle and fat. The Patrick-FABER test is one of the most common. You lie on your back while your doctor moves your hip into a combination of flexion, abduction, and external rotation, then presses on the bony prominence at the side of the hip. Pain reproduced in this position points toward the trochanteric bursa.
Your doctor may also watch you walk and ask you to stand on one leg. A Trendelenburg gait, where your pelvis drops on the opposite side with each step, suggests weakness in the hip abductor muscles that often accompanies trochanteric bursitis. During single-leg standing, a pelvic shift or drop of more than 2 centimeters over six seconds is considered a positive finding. These tests help distinguish bursitis from other sources of hip pain like stress fractures or problems inside the hip joint itself.
How Bursitis Is Told Apart From Tendonitis
Because bursae sit right next to tendons, the symptoms of bursitis and tendonitis overlap significantly. Both cause pain near a joint, and both can flare with certain movements. The distinction comes down to exactly where the pain and swelling are located relative to the anatomy. Bursitis tends to produce more diffuse swelling over the bursa, while tendonitis pain is usually more pinpoint along the tendon itself. Your doctor may ask you to stand, walk, or perform specific motions to see which structure is involved. In some cases, imaging is needed to confirm which one it is.
When Ultrasound or MRI Is Used
Most straightforward cases of bursitis don’t need imaging. But when the diagnosis is uncertain, symptoms don’t improve, or deeper structures need to be evaluated, your doctor may order an ultrasound or MRI.
Ultrasound is usually the first imaging choice for bursae close to the skin’s surface, like those at the knee, elbow, or shoulder. A healthy bursa is paper-thin. The largest bursa in the body, located between the shoulder’s rotator cuff and the overlying muscle, normally measures just 2 millimeters across. On ultrasound, an inflamed bursa shows up as an enlarged, fluid-filled pocket. Other signs include thickening of the bursa’s lining (uniform thickening suggests an acute flare, while irregular thickening points to chronic bursitis) and increased blood flow in the surrounding tissue.
MRI is reserved for deeper bursae that ultrasound can’t reach well, or when your doctor suspects something more complex. An inflamed bursa appears as a bright, fluid-filled structure on certain MRI sequences. MRI is particularly useful when a rotator cuff tear is suspected alongside shoulder bursitis, since fluid from inside the shoulder joint can leak through the tear and fill the bursa. A specialized version called an MR arthrogram, where contrast dye is injected into the joint, can highlight this abnormal connection. MRI is also helpful when infection has potentially spread to nearby bone.
X-rays don’t show bursae themselves, but they can rule out other problems. A stress fracture in the hip, for instance, can mimic bursitis pain. X-rays also reveal calcium deposits that sometimes form in or near bursae.
Fluid Analysis for Suspected Infection
When septic (infected) bursitis is a possibility, draining fluid from the bursa with a needle and sending it to a lab is the gold standard for diagnosis. This matters because septic bursitis and non-infectious bursitis can look nearly identical on exam. Both cause pain, swelling, redness, and warmth. Fever is more common with infection, but it’s not always present. One study found that a skin temperature difference of just 2.2°C between the affected side and the unaffected side was highly accurate for detecting infection, but this isn’t routinely measured in practice.
The fluid itself tells the story. In septic bursitis, white blood cell counts in the bursal fluid are elevated, with averages around 63,000 per cubic millimeter. Even a count above 2,000 has been shown to be 94% sensitive and 79% specific for infection. The type of white blood cells matters too: infected fluid is dominated by one type (polymorphonuclear cells), while non-infectious inflammation shows a different mix (mononuclear cells).
A Gram stain, which looks for bacteria under the microscope, is helpful when positive but unreliable when negative. It catches bacteria in only about half of confirmed septic bursitis cases. That’s why the fluid is also sent for culture, which takes longer but is more definitive. If the Gram stain is negative but the white blood cell count is above 50,000 and the clinical picture is concerning, the working diagnosis is still septic bursitis until the culture results come back.
Testing for Gout and Other Conditions
Fluid analysis also identifies crystal-related bursitis. When gout or a similar condition called pseudogout is the cause, examining the fluid under a polarized microscope reveals characteristic crystals. This is a straightforward finding that points directly to the diagnosis.
In cases where an autoimmune condition like rheumatoid arthritis may be driving the inflammation, the fluid typically shows elevated white blood cells, and additional blood tests specific to the suspected condition help confirm the diagnosis. These situations are less common but important to identify because they change the treatment approach entirely.