The clinical course of joint involvement is extremely variable:
- may be a mild, self-limiting mono- or oligoarthitis
- often an insidious symetrical polyarthritis
- the most aggressive disease results in rapid disability with systemic inflammation and a high mortality rate
Often the disease begins in:
- proximal finger joints
- wrists
Later inflammation spreads to:
- elbows
- shoulders
- knees
- ankles
- feet
Characteristic joint deformities include:
- ulnar deviation of the fingers due to subluxation at the metacarpophalangeal joints
- loss of finger function due to hyperextension of the PIP joints with fixed flexion of the DIP joints 'swan neck deformity'
- fixed flexion of the PIP joints with hyperextension of the DIP joints 'boutonniere' or Z deformity of the thumb