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.
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.
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:
- 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
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 PIP and MTP joints (especially 4th and 5th MTP)
- involvement of subtalar joint
- posterior calcaneal tubercle erosion
- hammertoe deformity
- hallux valgus
- erosion of the distal clavicle
- marginal erosions of the humeral head: the superolateral aspect is a typical location 2
- reduction in the acromiohumeral distance: "high-riding shoulder" due to subacromial-subdeltoid bursitis and high incidence of rotator cuff tear
- concentric loss of joint space, compared with osteoarthritis (OA) where there is a tendency for superior loss of joint space
- acetabular protrusio
- 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
The cervical spine is frequently involved in RA ( in approximately 50% of patients), whereas a thoracic and lumbar involvement are rare. Findings include:
- erosion of the dens
- atlantoaxial distance is more than 3 mm on a flexion radiograph
- atlantoaxial impaction (cranial settling): cephalad migration of C2
- erosion and fusion of uncovertebral (apophyseal joints ) and facet joints
- osteoporosis and osteoporotic fractures
- erosion of spinous processes
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
Ultrasound also has a role in guiding corticosteroid injections in this setting.
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 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
The differential for the skeletal manifestations of RA includes:
- 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.
- 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
- 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:
- seronegative spondyloarthritides
- Jaccoud arthropathy
- juvenile idiopathic arthritis
- lyme arthritis
- rheumatoid arthritis
- systemic lupus erythematosus
- erosive osteoarthritis
- osteoarthritis (mnemonic)
- primary cystic arthrosis of the hip
- rapidly destructive osteoarthritis of the hip
- secondary synovial osteochondromatosis
- miscellaneous disorders
- related articles
Ultrasound - musculoskeletal
- ultrasound (introduction)
- shoulder ultrasound
- elbow ultrasound
- wrist ultrasound
- hand ultrasound
- hip ultrasound
- knee ultrasound
- ankle/foot ultrasound
- paediatric musculoskeletal ultrasound
- skin/soft tissue ultrasound
- ultrasound of arthropathies
- 1. Brant WE, Helms CA. Fundamentals of diagnostic radiology. Lippincott Williams & Wilkins. (2007) ISBN:0781761352. Read it at Google Books - Find it at Amazon
- 2. Sommer OJ, Kladosek A, Weiler V et-al. Rheumatoid arthritis: a practical guide to state-of-the-art imaging, image interpretation, and clinical implications. Radiographics. 25 (2): 381-98. doi:10.1148/rg.252045111 - Pubmed citation
- 3. Rominger MB, Bernreuter WK, Kenney PJ et-al. MR imaging of the hands in early rheumatoid arthritis: preliminary results. Radiographics. 1993;13 (1): 37-46. Radiographics (abstract) - Pubmed citation
- 4. Dixey J, Solymossy C, Young A et-al. Is it possible to predict radiological damage in early rheumatoid arthritis (RA)? A report on the occurrence, progression, and prognostic factors of radiological erosions over the first 3 years in 866 patients from the Early RA Study (ERAS). J Rheumatol Suppl. 2004;69 : 48-54. J Rheumatol Suppl (link) - Pubmed citation
- 5. Greenspan A. Orthopedic imaging, a practical approach. Lippincott Williams & Wilkins. (2004) ISBN:0781750067. Read it at Google Books - Find it at Amazon
- 6. Weissleder R, Wittenberg J, Harisinghani MG. Primer of diagnostic imaging. Mosby Inc. (2003) ISBN:0323023282. Read it at Google Books - Find it at Amazon