- fusiform periarticular soft tissue swelling (result of effusion)
- regional osteoporosis (disuse and local hyperemia)
- widened joint space
- marginal + central bone erosion (base of 4th proximal phalanx most common)
- change in ulnar styloid (erosions) and distal radioulnar joint
- atlantoaxial dislocation
- giant synovial cysts
- late signs:
- flexion/extension contractures with ulnar subluxation/dislocation
- destruction/fusion of joints
- elevation of humeral heads (tear/atrophy of rotator cuff)
- resorption of distal clavicle
- erosion of superior margins of posterior portions of 3-5th ribs
- destruction/narrowing of disc spaces
- destruction of zygapophyseal joints without osteophyte formation
- resorption of spinous process
- protrusio acetabuli (from osteoporosis)
The radiographic hallmarks of rheumatoid arthritis are:
- soft tissue swelling : fusiform and periarticular. It represents a combination of joint effusion, oedema and tenosynovitis . This can be an early/only radiographic finding.
- osteoporosis that is initially juxta-articular, and later generalised. It is compounded by corticosteroid therapy and disuse.
- joint space narrowing : symmetrical or concentric.
- marginal erosions : due to erosion by pannus of the bony “bare areas”.
Hands and wrists
Diagnosis and follow-up of patients with RA commonly involves imaging of the hands and wrists. The disease tends to involve the proximal joints in a bilaterally symmetrical distribution.
There is predilection for:
- PIP and MCP joints (especially 2nd and 3rd MCP)
- ulnar styloid
As a rule, the DIP joints are spared.
Late changes include :
- subchondral cyst formation : destruction of cartilage presses synovial fluid into the bone
- subluxation causing
- hitchhiker’s thumb deformity
- carpal instability : scapholunate dissociation, ulnar translocation
- similar to the hands, there is a predilection for the DIP and MTP joints
- involvement of subtalar joint
- calcaneal erosions
- erosion of the distal clavicle
- marginal erosions of the humeral head
- reduction in the acromiohumeral distance : "high-riding shoulder"
- concentric loss of joint space (cf osteoarthritis where there is tendency for superior loss of joint space)
- acetabular protrusio
- joint effusion
- loss of joint space involving all three compartments
- lack of subchondral sclerosis and osteophytes (cf OA)
The cervical spine is frequently involved in RA, whereas thoracic and lumbar involvement is rare.
Findings include :