Diagnosis of osteoarthritis focuses on two major goals. When diagnosing osteoarthritis, the doctor must first differentiate osteoarthritis from other types of arthritis. It is also important to determine whether a patient has primary osteoarthritis or a secondary form of osteoarthritis associated with another disease or condition.
Early, accurate diagnosis of osteoarthritis is necessary so that appropriate treatment options can be considered. To diagnose osteoarthritis, your doctor will make assessments using:
Your medical history will include information about past medical conditions, allergies, treatments, and surgical procedures as well as current medical issues. Typically, at the first appointment with your doctor, you will be asked to fill out an extensive questionnaire about your medical history. You will also be asked about the symptoms you are experiencing including when they commonly occur and what makes the symptoms worse or better.
During the physical examination, your doctor will observe for any signs and symptoms which commonly are associated with osteoarthritis. The doctor will look for:
- Joint swelling
- Joint tenderness
- Decreased range of motion in joints
- Visible joint damage (i.e., bony growths)
- Pattern of affected joints
X-rays are typically used to confirm the diagnosis of osteoarthritis. X-rays can reveal osteophytes at the joint margins, joint space narrowing, and subchondral bone sclerosis. Subchondral bone is the layer of bone which is just below the cartilage. While MRI (magnetic resonance imaging) is a more sensitive imaging method, it is used less often than x-rays due to cost and availability. MRI scans show cartilage, bone, and ligaments.
Routine laboratory tests are usually normal so their value is in ruling out other types of arthritis, especially inflammatory types of arthritis, or establishing a baseline for monitoring treatment. Synovial fluid analysis also helps rule out other conditions.
American College of Rheumatology Criteria
The American College of Rheumatology has established clinical criteria for diagnosing primary osteoarthritis of the hand, hips, and knees:
Osteoarthritis of the Hand
- Hand pain, aching, or stiffness and;
- Hard tissue enlargement of two or more of 10 selected joints and;
- Fewer than three swollen MCP (metacarpophalangeal) joints and;
- Hard tissue enlargement of two or more DIP (distal interphalangeal) joints or deformity of two or more of 10 selected joints
The 10 selected joints include:
- Second and third DIP joints of both hands
- Second and third PIP (proximal interphalangeal) joints of both hands
- First CMC (carpometacarpal) joints of both hands
Osteoarthritis of the Hip
- Hip pain and;
- Femoral and/or acetabular osteophytes evident on x-ray or sedimentation rate less than or equal to 20 mm/hour and;
- Joint space narrowing evident on x-ray
Internal hip rotation of less than or equal to 15 degrees, morning stiffness in the hip lasting less than or equal to one hour, and age of 50 years or older are additional criteria which are useful for diagnosing osteoarthritis of the hip.
Osteoarthritis of the Knee
- Knee pain and;
- At least three of the following 6 criteria: 50 years of age or older, stiffness lasting less than 30 minutes, crepitus, bony tenderness, bony enlargement, no warmth to the touch
Laboratory findings which are useful to assessing knee osteoarthritis include sedimentation rate less than 40 mm/hour, rheumatoid factor less than 1:40, and synovial fluid examination showing clear, viscous fluid with a white blood cell count less than 2,000/mm3.
It is the doctor's job to be the diagnostician but it clearly is helpful if the patient understands why tests are being performed and what the results mean. If a patient understands the process from early symptoms to diagnosis to treatment plan, the patient will likely be more compliant and the outcome of treatment will likely be more successful.
Osteoarthritis. Differential Diagnosis. Primer on the Rheumatic Diseases. Edition 12. Published by the Arthritis Foundation.
The American College of Rheumatology Criteria for the Classification and Reporting of Osteoarthritis of the Hand. 1990. <http://www.rheumatology.org/publications/classification/oa-hand/1990_classification_%20oa_hand.asp>
The American College of Rheumatology Criteria for the Classification and Reporting of Osteoarthritis of the Hip. 1991. http://www.rheumatology.org/publications/classification/oa-hip/1991_classification_oa_hip.asp
Criteria for Classification of Idiopathic Osteoarthritis (OA) of the Knee. 1986. < http://www.rheumatology.org/publications/classification/oaknee.asp?aud=mem>