Rheumatoid arthritis (musculoskeletal manifestations)

Rheumatoid arthritis (RA) is a chronic multi-system disease with predominant musculoskeletal manifestations. Being a disease that primarily attacks synovial tissues, RA affects 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 manifestations.

Radiographic features

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

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:

  • 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
  • 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 affect the proximal joints in a bilaterally symmetrical distribution.

There is 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:

Feet
  • similar to the hands, there is a predilection for the PIP and MTP joints (especially 4th and 5th MTP)
  • involvement of subtalar joint
  • posterior calcaneal tubercle erosion
  • hammertoe deformity
  • hallux valgus
Shoulder
Hip
  • concentric loss of joint space, compared with osteoarthritis (OA) where there is a tendency for superior loss of joint space
  • acetabular protrusio
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 a thoracic and lumbar involvement are 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: 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:

  • osteoarthritis
    • involves the: DIPs, PIPs, 1st CMC joints
    • non-uniform joint space loss, subchondral sclerosis and osteophytes. 
    • soft tissue swelling: Heberden’s node (DIPs) and Bouchard node (PIPs).
    • no erosions and no anklylosis.
  • erosive osteoarthritis:
    • clinically acute inflammatory attacks (swelling, erythema, pain) in post-menopausal woman
    • 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 vs. MCP joint predominance in rheumatoid arthritis (RA)
    • starts with erosions in the margins and eventually involves the
      whole joint. classic: “pencil in cup” 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 (Reiter syndrome):
    • 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 MCP's: 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: 

Arthritides
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Article Information

rID: 12370
Section: Pathology
Synonyms or Alternate Spellings:
  • Rheumatoid arthritis (MSK)
  • Musculoskeletal manifestations of RA
  • Rheumatoid arthritis - musculoskeletal manifestations

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