Osteoarthritis may present as a chronic monoarthritis, oligoarthritis or polyarthritis. It is usually non-inflammatory and commonly affects large joints such as the hip and knee as well as small joints of the fingers and feet. The spine is another common site for osteoarthritic changes. Osteoarthritis may by symmetrical or asymmetrical. Patients with OA usually present with joint pain that worsens with activity and increases over the course of the day. Morning stiffness, if present, resolves within an hour. Pain is exacerbated by weight bearing and motion; this is usually relieved by rest. Signs of inflammation are usually absent as are systemic symptoms. Crepitus may be audible or palpable with both active and passive joint motion. Bony enlargement and joint deformity (e.g. "bowlegs" or varus knees) may be noted on physical examination along with restricted range of motion (rotation is often lost in the hips and flexion/extension in the knees).

The 1st metacarpophalangeal joint is a common site of osteoarthritis in middle-aged women (©ACR www.rheumatology.org)

Osteoarthritis is a clinical diagnosis. There are no laboratory tests that confirm the diagnosis. Plain radiographs, however, will often reveal characteristic findings indicative of OA. The classic radiological changes noted in osteoarthritis are:

• Joint space narrowing
• Osteophytes
• Bony sclerosis
• Subchondral cysts
• Malalignment

RA usually presents between the third and sixth decades. Patients often first notice joint stiffness, pain on movement and joint tenderness. The disease may develop slowly, over time and the diagnosis may not be obvious at first. Once involved, joints usually remain involved although not necessarily "active" as the disease course waxes and wanes. This differs from the "migratory" polyarthritis of systemic lupus erythematosus that affect different joints from flare to flare.

Prolonged (> 1 hour) morning stiffness is almost always present in RA patients; this symptom may also occur in other inflammatory arthritides but not in osteoarthritis. Although it may rarely present in just one joint, RA is usually seen as a symmetrical polyarthritis with a predilection for small, peripheral joints including the wrist, MCP and PIP joints of the hand. The thoracolumbar spine and DIP joints of the fingers and toes are not commonly involved.

Rheumatoid hand deformities (©ACR www.rheumatology.org)

Patients may initially complain of non-specific, systemic symptoms including fatigue, malaise and low-grade fever. Extra-articular symptoms vary widely. Rheumatoid nodules appear in 20-30% of patients; they are usually located on the extensor surfaces of the limbs and are generally asymptomatic. RA may also affect the eyes, lungs, heart, kidneys, and/or nervous system.

Many (80-90%) patients with RA test positive for Rheumatoid Factor (RF). RF is an IgM antibody directed at IgG. Although it is common in RA, RF may also be found in other inflammatory, autoimmune disorders such as Systemic Lupus Erythematosus (SLE). RF may also appear in healthy individuals and so is not a good predictor of the presence of RA. In individuals determined to have RA, the presence of this factor is associated with a worse prognosis, and so may influence decisions about treatment more than influencing the initial diagnosis. Review the 1987 Criteria for the Classification of Acute Arthritis of Rheumatoid Arthritis on the ACR webpage.