Imaging and Tests for Foot Pain
Noninvasive tests that allow your doctor to see inside your feet.
Imaging tests can allow your doctor to see the structures inside your foot noninvasively. The most common imaging tests to diagnose foot problems are:
X-ray (radiography). A standard X-ray is a simple test in which an X-ray beam (a form of electromagnetic radiation) is passed through the foot to create a two-dimensional picture of the bones that form the joint. A doctor can use X-rays to view:
- joint space. Narrowing of the space between the bones, which are normally covered by cartilage, can be a sign of arthritis and its severity.
- bone spurs. Bony overgrowths at the joint are a sign of osteoarthritis.
- fractures. Broken bones in feet and toes will show up on x-rays, however, small cracks in the bone may not.
In some cases, a contrast dye is injected into the foot to enable the doctor to better see the joint on X-ray. This is called arthrography.
Computerized axial tomography (CAT) scan. Also called a computed tomography (or CT) scan, this noninvasive test combines X-ray equipment with sophisticated computers to produce multiple images, which are combined to depict cross-sectional slices of internal structures. CT scans may be used to diagnose foot problems that don't show up on X-ray. They also show soft tissues, such as ligaments and muscles, more clearly than traditional X-rays, so they are more useful for diagnosing certain foot problems.
Magnetic resonance imaging (MRI). This procedure uses a strong magnet linked to a computer to create a picture of the internal structures in black and white and shades of gray. Because an MRI shows the soft tissues, as well as the bones, it is particularly useful for diagnosing injuries to the cartilage, tendons and ligaments, as well as areas of swelling. The test may also be used to determine the severity of tarsal tunnel syndrome.
Video fluoroscopy. This test, using an X-ray and a fluorescent screen, allows a doctor to view the internal structures and movements of the foot instantly, and to create an "X-ray movie" that can be viewed repeatedly.
Bone scan. This technique can be used to view stress fractures caused by repetitive trauma. It involves injecting a small amount of radioactive material into the bloodstream. The material collects in the bones, particularly in areas of new bone growth where fractures are healing, enabling doctors to see those areas with a scanner.
Electrodiagnostic tests. For diagnosing problems, such as tarsal tunnel syndrome, where there is compression of the nerve, a doctor may use electrodiagnostic tests, such as nerve conduction studies and electromyography. For nerve conduction studies, the doctor fastens electrodes to the ankle and foot, then sends small electric shocks to the nerves in the lower leg, ankle, and toes, and measures the speed of conduction of nerve fibers. In the electromyography, the doctor inserts thin needles into the muscle to record electrical activity. The electrical signals are viewed on a screen.
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