Which joints are commonly affected by Rheumatoid Arthritis (RA)?

Common Joints Affected by Rheumatoid Arthritis

Rheumatoid arthritis primarily affects the small joints of the hands and feet, particularly the metacarpophalangeal, proximal interphalangeal, wrist, and metatarsophalangeal joints, with a characteristic symmetric distribution pattern.

Most Commonly Affected Joints (In Order of Frequency)

1. Metacarpophalangeal (MCP) joints

   • Knuckle joints where fingers meet the hand
   • Often among the earliest joints affected

2. Proximal interphalangeal (PIP) joints

   • Middle joints of the fingers
   • Typically affected symmetrically

3. Wrists

   • Highly susceptible to early involvement
   • Early wrist involvement is associated with more severe disease progression 1
   • Carpal and pericapitate abnormalities are typically more prominent than in other forms of arthritis 2

4. Metatarsophalangeal (MTP) joints

   • Joints at the base of the toes
   • Often affected early in the disease course
   • Early MTP involvement predicts more severe disease outcomes 1

5. Knees

   • Commonly affected in established disease
   • Show significant progression over time 3

6. Ankles

   • Frequently involved in established disease

7. Shoulders

   • Often affected in early disease 1

8. Elbows

   • Less commonly involved than wrists and small joints

Less Commonly Affected Joints

• Temporomandibular joints

  • Can be involved even in early stages 1

• Cervical spine

  • May be affected early in the disease course 1
  • Requires monitoring due to potential serious complications

• Hip joints

  • Less frequently affected than other large joints 1

Characteristic Features of Joint Involvement

• Symmetry: Bilateral and symmetric joint involvement is a hallmark of RA 4
• Peripheral pattern: RA predominantly affects peripheral joints rather than axial joints 1
• Progression pattern: Joint damage typically starts with synovial proliferation and soft tissue swelling, followed by marginal erosions, and eventually joint space narrowing and deformities 4

Joints Rarely Affected

• Distal interphalangeal (DIP) joints
  • Minimal involvement compared to PIP and MCP joints 5
• Sacroiliac joints
  • Rarely involved in RA 5
• Lumbar spine
  • Infrequently affected 5, 1

Clinical Implications

• Early involvement of wrists and MTP joints is associated with more severe disease progression and poorer outcomes 1, 3
• By 10 years of disease, the wrists, knees, and small joints of the feet often show the most significant damage 3
• Hand and wrist radiographs provide a good indication of overall joint damage in RA, with strong correlation to total body joint involvement 3

Monitoring Considerations

• Regular assessment of joint involvement is crucial for disease activity monitoring
• Composite measures such as DAS28, SDAI, and CDAI should be used to assess disease activity 2
• Radiographic evaluation of hands and feet provides valuable information about disease progression 2, 3

Understanding the pattern of joint involvement in RA is essential for early diagnosis, monitoring disease progression, and evaluating treatment response.