Rheumatoid arthritis

early signs:

• 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 2^nd and 3^rd MCP)
• ulnar styloid
• triquetrum

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
  • ulnar deviation of the MCP joints
  • boutonierre and swan neck deformities
• hitchhiker’s thumb deformity
• carpal instability : scapholunate dissociation, ulnar translocation
• ankylosis

Feet

• similar to the hands, there is a predilection for the DIP and MTP joints
• involvement of subtalar joint
• calcaneal erosions

Shoulder

• erosion of the distal clavicle
• marginal erosions of the humeral head
• reduction in the acromiohumeral distance : "high-riding shoulder"

Hip

• concentric loss of joint space (cf osteoarthritis where there is tendency for superior loss of joint space)
• acetabular protrusio

Knee

• joint effusion
• loss of joint space involving all three compartments
• lack of subchondral sclerosis and osteophytes (cf OA)

Spine

The cervical spine is frequently involved in RA, whereas thoracic and lumbar involvement is rare.

Findings include :

• erosion of the dens
• atlanto-axial subluxation with cephalad migration of C2
• erosion and fusion of apophyseal joints
• erosion of spinous processes
• destruction of intervertebral disks
• osteoporosis and osteoporotic fractures

LINKS:

http://radiopaedia.org/articles/rheumatoid-arthritis

http://radiopaedia.org/articles/musculoskeletal-manifestations-of-rheumatoid-arthritis

Images: google images, www.radiopedia.org