Rheumatoid arthritis (musculoskeletal manifestations)

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Rheumatoid arthritis (RA) is a chronic multisystem disease with predominant musculoskeletal manifestations. Being a disease that primarily affects synovial tissues, i.e. synovial joints, tendons, and bursae.

Refer to the related articles for a general discussion of rheumatoid arthritis and for the particular discussion of its respiratory and/or cardiac manifestations.

Radiographic features

Regarding disease detection, as the early RA manifestations are non-osseous in nature, ultrasound and MRI have been shown to be superior to radiographs and CT. Plain radiography, however, remains the mainstay of imaging in the diagnosis and follow-up of RA 2. 

Plain radiograph

One large cohort study showed that radiographically demonstrable erosions were present in 30% of patients at diagnosis, and in 70% three years later 4.

The radiographic hallmarks of rheumatoid arthritis are:

  • marginal erosions; important early finding, in the “bare areas”, frequently in the radial side of the metacarpophalangeal (MCP) joints 7
  • soft tissue swelling
    • fusiform and periarticular; it represents a combination of joint effusion, oedema and tenosynovitis 5
    • this can be an early/only radiographic finding
  • osteoporosis: initially juxta-articular, and later generalised; compounded by corticosteroid therapy and disuse
  • joint space narrowing: symmetrical or concentric, uniform
Hands and wrists

Diagnosis and follow-up of patients with RA commonly involve imaging of the hands and wrists. The disease tends to affect the proximal joints in a bilaterally symmetrical distribution.

RA is a synovial-based process, with a predilection for:

  • PIP and MCP joints (especially 2nd and 3rd MCP)
  • ulnar styloid
  • triquetrum

As a rule, the DIP joints are spared.

Late changes include:

Elbow
  • joint effusion (elevated fat pads) 
  • joint space narrowing
  • periarticular erosions 
  • cystic changes
Feet
Shoulder
Hip
  • concentric loss of joint space, compared with osteoarthritis (OA) where there is a tendency for superior loss of joint space
  • acetabular protrusion
Knee
  • joint effusion
  • typically involves the lateral or non-weight bearing portion of the joint
  • loss of joint space involving all three compartments
  • lack of subchondral sclerosis and osteophytes, compared with OA
  • prepatellar bursitis
Spine

The cervical spine is frequently involved in RA (in approximately 50% of patients), whereas thoracic and lumbar involvement is rare. Findings include:

Ultrasound

Sonography can assess the soft tissue manifestations of RA. In particular:

  • synovial proliferation and inflammation of the superficial joints
  • tenosynovitis: extensor carpi ulnaris tendon involvement is common in early disease and may lead to erosion of the ulnar styloid 2
  • bursitis

Ultrasound also has a role in guiding corticosteroid injections in this setting.

CT

CT is not routinely used in the evaluation of peripheral RA. It has applications in imaging of the spine, and peri-operative assessment 2.

MRI

MRI is particularly sensitive to the early and subtle features of RA.

Commonly used sequences include T1-weighted contrast-enhanced spin-echo with fat saturation and T2-weighted spin-echo or gradient-echo sequences 2.

Features of RA best demonstrated with MRI include 2:

  • synovial hyperaemia: an indication of acute inflammation
  • synovial hyperplasia (rice bodies)
  • pannus formation
  • decreased thickness of cartilage
  • subchondral cysts and erosions:
    • MRI is much more sensitive than radiography
    • it is thought that subchondral cysts in RA eventually progress to erosions (i.e. constitute "pre-erosions")
    • contrast enhancement may distinguish erosions or pre-erosions from degenerative subchondral cysts
  • juxta-articular bone marrow oedema
  • joint effusions

Differential diagnosis

The differential for the skeletal manifestations of RA includes:

  • degenerative osteoarthritis
    • involves the: DIPs, PIPs, 1st CMC joints
    • non-uniform joint space loss, subchondral sclerosis, and osteophytes
    • soft tissue swelling: Heberden node (DIPs) and Bouchard node (PIPs)
    • no erosions and no ankylosis
  • erosive osteoarthritis
    • clinically acute inflammatory attacks (swelling, erythema, pain) in postmenopausal women
    • typically involves the DIPs, PIPs, 1st CMC joint 6, but not MCP joints or large joints
    • classic central erosions, possible ankylosis
  • psoriatic arthritis (PsA)
    • commonly involves the hands and there is an interphalangeal predominant distribution in PsA compared to MCP joint predominance in rheumatoid arthritis (RA)
    • starts with erosions in the margins and eventually involves thewhole joint, the classic changes being the pencil-in-cup deformity and bone proliferation (unlike RA)
    • osteoporosis not a feature in PsA
    • MRI dynamic enhancement pattern may differentiate PsA from RA at 15 minutes
  • reactive arthritis
    • a predilection for the lower limb
    • osteopenia and then osteoporosis, uniform joint space loss, subchondral cyst formation, subluxations, marginal erosions but no bone formation
    • symmetrical involvement of the: PIPs, MCPs, and carpal bones
  • systemic lupus erythematosus (SLE)/Jaccoud arthropathy
    • joint space loss, subchondral sclerosis, osteophyte, and ulnar deviation of the phalanges without erosions
  • calcium pyrophosphate dihydrate (CPPD) arthropathy
    • usually only affects the MCPs: symmetric joint space narrowing, subchondral cysts, and osteophytes
    • unlike RA: chondrocalcinosis and no erosions 
  • gout
    • usually in older men
    • punched out erosions usually with a sclerotic border and overhanging edges, tophi most commonly involves the 1st MTP (which is known as podagra)

Site-specific differential diagnosis: 

  • -<a title="Subtalar joint" href="/articles/subtalar-joint">subtalar joint</a> involvement</li>
  • +<a href="/articles/subtalar-joint">subtalar joint</a> involvement</li>
  • -<li><a title="Hallux valgus" href="/articles/hallux-valgus">hallux valgus</a></li>
  • +<li><a href="/articles/hallux-valgus">hallux valgus</a></li>
  • -<li>reduction in the <a title="Acromiohumeral distance" href="/articles/acromiohumeral-interval">acromiohumeral distance</a>: "<a href="/articles/high-riding-shoulder">high-riding shoulder</a>" due to subacromial-subdeltoid bursitis and high incidence of <a href="/articles/rotator-cuff-tear">rotator cuff tear</a>
  • +<li>reduction in the <a href="/articles/acromiohumeral-interval">acromiohumeral distance</a>: "<a href="/articles/high-riding-shoulder">high-riding shoulder</a>" due to subacromial-subdeltoid bursitis and high incidence of <a href="/articles/rotator-cuff-tear">rotator cuff tear</a>
  • -<a title="Cranial settling" href="/articles/basilar-invagination">atlantoaxial impaction (cranial settling)</a>: cephalad migration of C2</li>
  • +<a href="/articles/basilar-invagination">atlantoaxial impaction (cranial settling)</a>: cephalad migration of C2</li>
  • -<a title="Osteoporosis" href="/articles/osteoporosis-3">osteoporosis</a> and <a title="Osteoporotic compression fracture" href="/articles/spinal-compression-fracture">osteoporotic fractures</a>
  • +<a href="/articles/osteoporosis-3">osteoporosis</a> and <a href="/articles/spinal-compression-fracture">osteoporotic fractures</a>
Images Changes:

Image 11 CT (bone window) ( create )

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