Which joints are commonly affected by rheumatoid arthritis?

Common Joints Affected by Rheumatoid Arthritis

Rheumatoid arthritis characteristically affects the small joints of the hands and feet in a symmetric pattern, specifically targeting the metacarpophalangeal (MCP) joints, proximal interphalangeal (PIP) joints, wrists, and metatarsophalangeal (MTP) joints, while typically sparing the distal interphalangeal (DIP) joints. 1, 2

Small Joints of the Hands

• MCP joints are involved in approximately 27-29% of cases and represent a hallmark of early rheumatoid arthritis 2
• PIP joints demonstrate involvement in approximately 29-33% of cases 2
• The wrist is one of the most frequently affected sites, showing both early involvement and the most progression over time 3, 4
• DIP joints are characteristically spared in rheumatoid arthritis, which helps distinguish it from osteoarthritis and psoriatic arthritis 1, 2

The 2010 ACR/EULAR classification criteria specifically include MCP and PIP joints in the small joint category while explicitly excluding DIP joints from assessment, underscoring their diagnostic importance. 2

Small Joints of the Feet

• MTP joints are preferential sites of involvement and are among the most commonly affected joints in early disease 3, 5
• The small joints of the feet show frequent complete destruction in advanced disease 4

Large Joints Commonly Affected

• Knees are frequently involved and show significant progression of damage over the disease course 6, 4
• Shoulders, including both glenohumeral and acromioclavicular joints, are commonly affected 6
• Elbows are among the frequently involved large joints 3, 6
• Ankles demonstrate regular involvement 7, 5
• Hips can be affected, though less commonly than other large joints 5

The 2010 ACR/EULAR criteria assign different point values based on joint involvement: 1-3 small joints score 2 points, 4-10 small joints score 3 points, and more than 10 joints (including at least one small joint) score 5 points. 1, 8

Pattern of Joint Involvement

• Symmetric involvement is the hallmark of rheumatoid arthritis, distinguishing it from other inflammatory arthritides 3, 5
• Bilateral hand, wrist, and foot involvement provides a reasonable picture of overall disease progression 4
• The wrist and small joints of the feet are most affected initially, while during disease progression, the wrist, knee, and MCP joints show the most advancement 4

Joints Typically Spared

• DIP joints are rarely involved in rheumatoid arthritis 3
• The first carpometacarpal joint is typically spared 1
• The first MTP joint is typically spared 1
• Sacroiliac joints are rarely involved 3
• The lumbar spine is rarely affected 3

This sparing pattern is diagnostically useful, as DIP involvement suggests alternative diagnoses such as osteoarthritis (with bony Heberden's nodes) or psoriatic arthritis. 2

Clinical Presentation

• Morning stiffness lasting at least 1 hour before maximal improvement is characteristic and related to disease activity 3
• Joint swelling and tenderness to palpation with severe motion impairment are typical articular manifestations 3
• Soft tissue swelling rather than bony enlargement characterizes inflammatory involvement 2
• Fusiform soft tissue swelling is a characteristic finding on examination 5

Periarticular Involvement

• Tendon and bursal involvement are frequent and often clinically dominant in early disease 3
• Tenosynovitis and bursitis can be presenting manifestations 3

The synovium of bursae and tendon sheaths is affected by the same inflammatory process, and ultrasound is superior to clinical examination for detecting these periarticular manifestations. 1, 5

Progression Patterns

• Patients with positive rheumatoid factor are more than 70% likely to develop joint damage or erosions within 2 years of disease onset 5
• Seropositive patients have more initial damage and a greater rate of progression 4
• Progression occurs in both initially normal and abnormal joints 4
• By 10 years, only 16.5% of joint groups show no damage 4