Diagnosis of osteoarthritis (OA) begins with a review of the patient’s medical history. Focus will be placed on any familial arthritic conditions, previous injuries or surgeries and general use of the joints. A pain assessment may also be used to help identify the nature and severity of the condition. A physical examination that concentrates on the areas of complaint may be completed by a rheumatologist (specialist in arthritis and other inflammatory diseases) or other physician.

The physician will examine the joints and surrounding areas for:

• Pain or tenderness
• Swelling or stiffness
• Reduced range of motion or flexibility
• Instability or difficulty bearing weight
• Crepitus (grating or crackling sound or feeling)
• Bony lumps, nodes or growths

Most diagnostic examinations where OA is suspected will include imaging studies, such as x-rays, MRI (magnetic resonance imaging) or a bone scan.

Although x-rays and MRI are good indicators of damage to joints, the degree of damage may be unrelated to the intensity of a patient’s symptoms. Physicians use the studies to look for:

• Bony outgrowths (osteophytes)
• Narrowing of the joint capsule
• Hardening or formation of cysts

Laboratory tests cannot diagnose OA. However, blood tests may be used to rule out other forms of arthritis and diseases if needed. These tests may include:

• Rheumatoid factor (RF) test. May indicate rheumatoid arthritis (RA) or other autoimmune conditions.
  
  
• Erythrocyte rate (ESR or sed rate). An elevated level in this blood test indicates inflammation, but can be caused by many forms of inflammation or infection. It may be combined with the physician's clinical findings to confirm conditions such as polymyalgia rheumatica.
  
  
• C reactive protein test. An elevated level of this protein produced by the liver suggests an inflammatory disease, such as RA.

Other blood tests may indicate the presence of uric acid, a sign of gout, or the presence of a genetic marker that is seen with some other forms of arthritis.

In some cases, a biopsy or synovial fluid analysis may be completed. These tests may identify or rule out other conditions but cannot diagnose OA.

The combination of findings from lab tests, x-rays and a physical examination may provide a physician with enough information to diagnose OA.