To diagnose a bone or joint infection, your doctor first performs a physical exam, looking for any open sores or areas of tenderness, swelling, and redness. He or she may ask if you’ve had any recent infections or surgery, of if you’ve experienced any pain or decreased range of motion in the affected limb or joint.
The doctor may also order tests to look for the presence of bacteria and assess the extent of the condition.
Doctors may use blood tests to determine if you have an infection, and, if so, what type of bacterium or fungus is causing it. Information from this test helps the doctor select the most effective antibiotic.
Blood tests are also used to detect sepsis, a potentially life-threatening complication of an infection that reduces blood flow to major organs and body systems, such as the lungs, kidneys, liver, and central nervous system, causing them to shut down.
X-rays use electromagnetic radiation to create pictures of the body. They may be used to identify the exact location of an infection. X-rays are also used to look for any changes in the bone or joint that may indicate a chronic infection.
To better view the structure of a bone or joint or the soft tissues, such as cartilage and muscle, a doctor may order an MRI scan, which uses a magnetic field and radio waves to create computerized, three-dimensional images of structures in your body.
Before the test, the doctor may inject a contrast dye into your vein. This dye helps to enhance the MRI image.
A CT scan uses X-rays and a computer to create detailed, three-dimensional, cross-sectional images of your tissues and internal organs. A CT scan reveal bone or joint damage caused by an infection.
Your doctor may give you a contrast agent, injected into a vein, to enhance the quality of the image.
The doctor may recommend a bone scan instead of an MRI scan if you have a medical implant, such as a pacemaker, which may affect the magnets in the scanner.
During a bone scan, the doctor injects a substance called a tracer into a vein in your arm. The tracer travels through your bloodstream and into your bones, where it is absorbed by areas that are growing more rapidly. A specialized camera, similar to an X-ray machine, takes pictures of the tracer.
Areas of bone growth or repair show up as bright spots on the image. This can indicate an infection.
If your doctor suspects you have a bone or joint infection, he or she may perform a tissue culture to determine the type of bacteria causing it. The doctor removes some fluid from a wound over an infected bone. Alternatively, the doctor may take a tissue sample from within the infected bone or joint. The doctor sends this specimen to a laboratory for examination.
To obtain a tissue sample, the doctor rubs a swab over the surface of the wound. He or she may use a needle to remove a piece of tissue from an infected bone.
The doctor may also insert a needle into the joint to remove a sample of the synovial fluid found there. Synovial fluid is usually clear, but if it’s infected it may be cloudy and thick.
During these procedures, you may be given a sedative to help you relax.
After a doctor identifies a bone or joint infection through imaging studies, he or she may biopsy the affected area to determine which bacteria are involved. This helps him or her choose the best course of treatment.
Your doctor may also perform a bone biopsy if he or she suspects that you have an infection that isn’t showing up clearly on imaging tests. This procedure is similar to a tissue culture, in which a doctor uses a needle to remove a sample from the affected area.
Doctors may perform a bone biopsy and tissue culture at the same time.
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