 [ Symptoms ] how is osteoarthritis diagnosed [ Disease ] doctors make a diagnosis of oa based on a physical exam and history of symptoms the diagnosis of osteoarthritis is based on a combination of the following factors * a description of symptoms * the location and pattern of pain * certain findings in a physical examination x rays may be used to confirm a diagnosis and to make sure that no other type of arthritis is present most people over age 60 reflect the disease on x ray about a third of patients have actual symptoms sometimes blood tests are administered while blood tests cannot point to anything in particular that can help a doctor confirm the presence of oa the tests can help the doctor determine the presence of a different type of arthritis if fluid has accumulated in the body is joints the doctor may remove some of the fluid with a process called joint aspiration and may examine the fluid under a microscope to rule out other diseases