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Posted by email@example.com, 8/26/04 at 10:49:19 AM.
Rheumatoid arthritis is the most common purely erosive inflammatory
arthropathy. Rheumatoid arthritis is generally symmetric and affects
proximal joints. There are no proliferative erosions as in erosive OA,
psoriatic or Reiter's arthritides. Rheumatoid arthritis rarely includes
any productive bone such as periostitis, enthesopathy, and osteophyte
formation unless there is secondary osteoarthritis present. Rheumatoid
factor is positive in 90-95% of the cases. Early in rheumatoid
arthritis the RF may be falsely negative, and in older patients, the RF
may be falsely positive. [MSK: The Requisites, 2nd edition, Manaster et
The characteristic radiographic features of rheumatoid arthritis
include soft-tissue swelling, periarticular osteoporosis, joint space
narrowing, articular erosions, and marginal erosions. The marginal
erosions are caused by the extension of pannus into synovial pockets
overlying regions devoid of articular cartilage (which would normally
protect against the toxic debris and inflammatory pannus in the
synovial fluid). [Musculoskeletal Imaging: Case Review, Josephy Yu,
Within the Wrist: Early RA will
demonstrate erosions in the distal radioulnar joint, ulnar styloid,
radial styloid, and triquetro-pisiform joint (the latter are best seen
on ball-catcher's view). Typically, the next erosions and joint space
narrowing will occur in the carpal bones and MCP joints. Ligamentous
rupture can lead to wrist instability resulting in ulnar translocation
of entire carpus, scapholunate instability, and dorsal and volar
flexion carpal instability (DISI and VISI).
Within the Elbow: Diffuse
involvement of joint with extensive erosion in olecranon articulation
and joint space narrowing with trochlea of humerus seeming to "dig
into" olecranon. Joint effusion and olecranon bursitis may also occur.
Within the Shoulder:
Glenohumeral joint space narrowing with marginal erosions within the
humeral head. Ligamentous/tendinous injury results in rotator cuff
degeneration with a "high-riding" humeral head. Also look for lysis of
the lateral clavicle and erosion at the insertion of the
Within the Spine: The cervical
spine is commonly affected; particularly look for C1-C2 involvement
which can have catastrophic consequences. For instance, pannus
formation near the odontoid can cause erosions in the odontoid and
ligamentous laxity of the transverse ligaments. The latter results in
increased predental space (greater than 2.5-3 mm which is upper limit
of normal in adults) which can result in canal stenosis. Alternatively,
the pannus itself can proliferate and directly compress the spinal
cord. Also, ligamentous destruction can result in atlantoaxial
impaction (ie. dens goes up into the foramen magnum along with Mr.
Cord--Mr. Cord doesn't like that). Other findings include erosions
within the facet joints.
And courtesy of Dr. Richardson:
Within the Hip: Axial joint
space narrowing leading to protrusio deformity at the severe end of the
spectrum, diffuse osteoporosis, lack of osteophyte formation unless
secondary OA occurs. In contradistinction, OA usually results in
superolateral (ie. weight-bearing) acetabular joint space narrowing,
normal bone density and osteophyte formation.
Within the Knee: Joint space
narrowing, osteoporosis, marginal erosions, without osteophyte
formation unless there is secondary OA (do you see a recurring theme?).
There may be a joint effusion with fluid tracking into the
semimembranosus-gastrocnemius bursa (AKA Baker's or popliteal cyst).
Occasionally there will also be patellar tendon rupture.
Within the Feet: MTP joint
erosions early on, particularly of the 5th MTP. Toe deformities that
result include lateral deviation at the MCPs and hammer toes. Also look
for retrocalcaneal bursitis with erosions in the posterior calcaneus;
the retrocalcaneal fluid can obliterate the pre-Achilles fat pad (AKA
Krager's fat pad).
- Manaster BJ, Disler DG, May DA. Musculoskeletal Imaging: The Requisites. Mosby 2002
- Yu J. Musculoskeletal Imaging: Case Review. Mosby 2001.
- Brant WE, Helms CA. Fundamentals of Diagnostic Radiology, 2nd edition. Lippincott Williams & Wilkins 1999