X-rays aren't helpful in diagnosing plantar fasciitis, because they do not show ligaments clearly. But your doctor might take X-rays if he or she suspects a stress fracture, bone cyst, or other foot or ankle bone problems. X-rays may show whether a heel spur is present, but a bone spur does not necessarily mean that a person has plantar fasciitis.
If the diagnosis is not clear, you may have other tests. Tests that are done in rare cases include MRI, blood tests, bone scans, and vascular testing, which can evaluate blood flow in the foot and lower leg. If your doctor suspects nerve entrapment, you may have neurological testing.