Your doctor can usually determine if you have tennis elbow by talking to you about the history of your symptoms, daily activities, and past injuries. You'll have a physical exam too.
X-rays aren't usually needed for diagnosis of tennis elbow but can sometimes rule out other causes of elbow pain, such as arthritis, signs of another type of injury, or a buildup of calcium crystals in a tendon or ligament. X-rays can show unusual bone structure that might cause soft-tissue damage (such as to tendons or muscles), but they don't show soft tissues very clearly. If your elbow pain isn't severe and can't be linked to a specific injury, your doctor may recommend starting treatment without doing X-rays to see whether the problem clears up in a few weeks.
Most cases of plantar fasciitis are diagnosed by a health care provider based on your symptoms and a physical exam in which he or she will press on the bottom of your feet -- the area most likely to be painful in plantar fasciitis, inflammation of the thick, fibrous band of tissue (''fascia'') that reaches from the heel to the toes and supports the muscles and arch of the foot. He or she may suggest that you have an X-ray of your foot to verify that there is no stress fracture causing your pain.
If nonsurgical treatment (such as rest, the use of ice and anti-inflammatory drugs, rehabilitation exercises, and changing or stopping certain activities) hasn't helped relieve elbow pain, or if the diagnosis is unclear, other tests may be helpful.
MRI can show problems in soft tissues such as tendons and muscles.
Arthroscopy allows the doctor to see inside the elbow and get information that can be used with what he or she knows from your X-rays or physical exam. (Doctors can surgically treat tennis elbow with arthroscopy.)
Bone scans are done in rare cases. They can show stress fractures in the bone or certain disease conditions, such as a tumor or infection.