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Joseph R. Perno, MD, PhD, and 
Neil Roach, MD

OsteOarthritis and inflammatOry 
arthritis

  1.  What imaging modality is best for diagnosis and follow-up of arthritic diseases?

Plain films are the mainstay for arthritis imaging. They are easy to obtain and give high-resolution information 

about cortical bone changes such as erosions, joint space narrowing, and osteophytes. The sensitivity of plain 

radiographs to detect early changes of rheumatoid arthritis (RA) is limited, however. Magnetic resonance 

imaging (MRI) has been shown to be sensitive to early changes, such as marrow edema, erosions, and synovial 

inflammation.

  2.  What is the difference between an inflammatory arthritis and a degenerative 

arthritis?

Inflammatory arthritides are diseases of the synovium, which subsequently produce erosive changes of the adjacent 

bones. Examples of inflammatory arthritis include RA and psoriatic arthritis. Degenerative arthritis/osteoarthritis is 

secondary to articular cartilage damage from repetitive microtrauma that occurs throughout life, although multiple other 

factors, such as heredity, nutrition, metabolic factors, preexisting articular disease, and body habitus, may contribute to 

development of the radiographic features of osteoarthritis, which include osseous proliferation, joint space narrowing, 

and subchondral sclerosis.

  3.  Which joints are most often affected 

in RA?

RA has a predilection for the carpal/

tarsal, carpometacarpal/tarsometatarsal, 

metacarpophalangeal/metatarsophalangeal, 

and proximal interphalangeal joints (

Fig. 40-1

). 

In adults, the distal interphalangeal joints rarely 

are affected. Joint involvement tends to be 

bilateral, but not always symmetric. Generally, the 

metacarpophalangeal and the metatarsophalangeal 

joints are affected first.

  4.  What portion of the spine does RA 

most commonly affect?

In the cervical spine, RA commonly causes 

atlantoaxial (C1 to C2) subluxation because of 

laxity of the transverse ligament and pannus 

formation. Other disease entities may affect this 

region of the cervical spine, including gout, calcium 

pyrophosphate dihydrate (CPPD) crystal deposition 

disease, and hydroxyapatite deposition disease. 

Some of these other disease processes may cause 

erosions of the dens, atlantoaxial subluxation, and 

radiopaque calcifications.

  5.  Can RA affect nonarticular structures?

Yes. Retrocalcaneal bursitis is common and is detected when the retrocalcaneal fat at the posterior-superior aspect of 

the calcaneus is obscured by edema. It is often accompanied by bone erosion.

  6.  How do inflammatory arthritides affect cartilage?

Inflammatory arthritides are a chronic synovitis, eroding bone that is “unprotected” by cartilage. These changes are 

noted first at the margins of joints, where cartilage is thinnest. Cartilage is also eroded by the joint inflammation, but 

tends to erode in an even and uniform manner.

Figure 40-1. 

Ulnar deviation of the metacarpals is noted in this patient 

with RA. There is a typical marginal erosion of the metacarpal head 

(arrow).

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OsteOarthritis and inflammatOry arthritis

  7.  What finding, which is common in osteoarthritis, is virtually never seen  

with RA?

The presence of significant osteophytes (productive bone changes) is not consistent with the diagnosis of RA. A joint that 

has been destroyed by RA may then develop osteoarthritis, however, owing to cartilage loss.

  8.  What additional joint findings are seen with RA?

Subluxations and malalignments at the metacarpophalangeal and metatarsophalangeal joints are typical. The 

subluxations tend to deviate the phalanges in the ulnar direction (see 

Fig. 40-1

).

  9.  Where are the swan neck and boutonnière deformities located?

The chronic inflammatory changes of RA in the joints of the fingers produce retraction of the tendons. The swan 

neck deformity is caused by hyperextension of the proximal interphalangeal joint with simultaneous flexion of the 

distal interphalangeal joint. If you try this manipulation on yourself, you will recognize the reason for the name. The 

boutonnière (or buttonhole) deformity is caused by hyperextension of the distal interphalangeal joint with simultaneous 

flexion of the proximal interphalangeal joint.

 10.  When can RA be confused with other arthritides?

Severe erosions of the subchondral bone may develop late in RA after the cartilage is destroyed and may give an 

appearance similar to erosive osteoarthritis.

 11.  What joints are typically affected by osteoarthritis?

Osteoarthritis most often affects the proximal and distal interphalangeal joints of the hands and the major weight-

bearing joints—the hips and the knees. In addition, the carpal joints at the base of the thumb are commonly affected 

(trapeziometacarpal and scaphotrapeziotrapezoidal joints). The most commonly affected joint in the foot is the first 

metatarsophalangeal joint. Any joint damaged by trauma that results in an irregular articular surface can become 

prematurely arthritic.

 12.  Where are Heberden and Bouchard nodes located?

•

Heberden nodes are osseous outcroppings involving the distal interphalangeal joints.

•

Bouchard nodes involve the proximal interphalangeal joints.

Bouchard and Heberden nodes are physical examination signs of hand osteoarthritis.

 13.  Which joints are rarely involved in 

primary osteoarthritis?

Involvement of the radiocarpal, pan-carpal, and 

metacarpophalangeal joints is rare in osteoarthritis, 

but is common in RA and psoriatic arthritis.

 14.  What are the hallmarks of 

osteoarthritic change in a joint?

Erosive arthritides have uniform cartilage loss, 

whereas degenerative osteoarthritis results in 

segmental cartilage loss. In small joints, such 

as joints in the fingers, the loss may seem to 

be uniform. The layer of bone just beneath the 

cartilage is called the subchondral bone. When 

exposed to increased stress, this layer becomes 

sclerotic. As this process continues, the cartilage 

and the underlying bone can become eroded, 

producing cystlike pockets in the bone, called 

geodes. At the edge of a joint where the cartilage 

is thinnest, exposed bone becomes hypertrophic, 

resulting in irregular or pointed outcroppings of 

bone, called osteophytes.

 15.  What is erosive osteoarthritis?

Erosive osteoarthritis is a form of osteoarthritis that 

is sometimes called inflammatory osteoarthritis 

(

Fig. 40-2

). Although the joint distribution is the 

Figure 40-2. 

Erosive osteoarthritis involving the distal interphalangeal 

joints, with a combination of productive and erosive changes. Note the 

classic “gull wing” deformity of the distal interphalangeal joint (arrow).

OsteOarthritis and inflammatOry arthritis

281

musculOskeletal radiOlOgy

same as in typical osteoarthritis, the erosive changes are more severe, and there is soft tissue swelling, which may give 

a similar appearance to RA or psoriatic arthritis. These changes involve the subchondral cortex in the main portion of the 

joint, however, rather than the peripheral “bare areas.” Ultimately, the phalangeal joints may become fused.

 16.  Name the seronegative spondyloarthropathies.

Seronegativity refers to the absence of rheumatoid factor in blood tests of patients who present with inflammatory 

arthritis. This group of diseases includes psoriatic arthritis, reactive arthritis (Reiter syndrome), ankylosing spondylitis (AS), 

and enteropathic arthritis (associated with inflammatory bowel diseases such as Crohn disease and ulcerative colitis).

 17.  What mnemonic can be used to remember the triad of symptoms seen with reactive 

arthritis (also known as Reiter syndrome)?

“Can’t see (uveitis), can’t pee (urethritis), can’t bend your knee (arthritis).”

 18.  What are the different presentations of psoriatic arthritis?

Psoriatic arthritis tends to involve the terminal interphalangeal joints of both hands; this is in contrast to RA, which more 

commonly involves more proximal joints in the hands and wrists. A second presentation pattern of psoriatic arthritis 

may involve multiple joints of a single hand. The third pattern involves only the joints of a single ray. The appearance is a 

combination of erosive and productive bony changes. The erosive changes occur at the peripheral bare areas, similar to RA. 

Psoriatic arthritis also has productive bone formation adjacent to the joint, however, typically in an exuberant and irregular 

manner. Although the clinical symptoms of psoriatic arthritis develop in 30% to 40% of patients with psoriasis, psoriatic arthritis 

usually does not occur concomitantly with the dermatologic diagnosis and may take 10 years or longer to manifest. It has been 

estimated, however, that 10% to 15% of patients have musculoskeletal complaints as the first manifestations of psoriasis.

 19.  What is the “pencil-in-cup” deformity?

The advanced erosive changes seen in psoriatic arthritis can produce a pointed appearance of the proximal phalanx that 

then pushes into the base of the more distal phalanx and deforms it to look like a cup.

 20.  Does AS have a specific pattern of 

joint involvement?

AS preferentially involves the sacroiliac joints and 

lumbar spine, and then may advance craniad to 

involve the thoracic and cervical spine. Ankylosis 

refers to the bony fusion of the opposing surfaces, 

which results in sclerosis and loss of the normal 

sacroiliac joint cartilage space (

Fig. 40-3

). Focal 

cortical irregularities at the anterior margin of the 

superior and inferior discovertebral junctions are 

considered early and significant features of AS 

seen on conventional radiographs and have been 

termed Romanus lesion. The MRI correlate has 

been described and is termed the “MRI corner” 

sign. Healing of the Romanus lesion leads to 

sclerosis at the end-plate corners and has been 

termed the “shiny corner” sign.

 21.  What does the term bamboo spine 

describe?

AS produces syndesmophytes, which are osseous bridges of the intervertebral disc spaces along Sharpey fibers in 

the anulus fibrosus. Combined with fusion of the facet joints and ossification of the longitudinal spinal ligaments, the 

appearance is similar to that of a stick of bamboo.

 22.  What is the radiologic appearance of gout?

Gout classically involves the first metatarsophalangeal joint. Other joints of the hand and foot can also be affected, 

however. Although more than one joint may be involved, it does not tend to be symmetric as other inflammatory 

arthritides can be. The classic appearance of a gout erosion is termed the overhanging margin, with a rim of eroded 

cortex hanging over a soft tissue density called a tophus. Tophi are soft tissue deposits of monosodium urate crystals 

that may occur anywhere, particularly in the dorsal aspect of the foot and the extensor aspect of the elbow.

 23.  What is pseudogout?

Pseudogout is not a radiographic diagnosis; it refers to a goutlike clinical syndrome with acute attacks of intermittent pain.

Figure 40-3. 

AS causes fusion of the sacroiliac joint. When this joint 

fuses, the normally dark-appearing cartilage becomes replaced by bone 

matrix (double arrows).

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OsteOarthritis and inflammatOry arthritis

 24.  What are the differences between 

pyrophosphate arthropathy and 

CPPD crystal deposition disease?

CPPD crystal deposition disease is a specific 

term for a disorder characterized by the exclusive 

presence of CPPD crystals in and around joints. 

Pyrophosphate arthropathy describes a pattern 

of joint damage that is secondary to CPPD crystal 

deposition disease. Although the radiographic 

changes of pyrophosphate arthropathy may 

be similar to osteoarthritis (osteophytosis, 

subchondral sclerosis, and joint space narrowing), 

there is a tendency to develop prominent 

subchondral cystic changes and decreased 

osteophytosis (as seen in osteoarthritis), and 

it tends to involve non–weight-bearing joint 

spaces, such as the shoulder, patellofemoral, and 

radiocarpal joints. It also tends to be symmetric. 

In the hand, CPDD crystal deposition disease 

tends to involve the metacarpophalangeal joints, 

particularly the second and third, but spares 

the interphalangeal joints. The subchondral 

bone becomes involved by multiple cystlike 

lucencies that can eventually lead to collapse 

of the articular surface (scapholunate advanced 

collapse wrist).

Calcium pyrophosphate crystals tend to deposit within fibrocartilage. The menisci of the knee, triangular fibrocartilage 

of the wrist, labra of the acetabulum and glenoid, symphysis pubis, and anulus fibrosus of the intervertebral disc are 

common sites. These cartilage calcifications are termed chondrocalcinosis (

Fig. 40-4

). These deposits may also affect 

the hyaline cartilage, which becomes a more specific radiologic marker for the disease. Soft tissue calcification is also 

common in tendons, bursae, and synovium.

B

iBliography

[1]  A. Brower, Arthritis in Black and White, Saunders, Philadelphia, 1988.

[2]  J.M. Farrant, P.J. O’Connor, A.J. Grainger, Advanced imaging in rheumatoid arthritis, part 1: synovitis, Skeletal Radiol. 36 (2007) 269–279.

[3]  A. Feydy, F. Lioté, R. Carlier, et al., Cervical spine and crystal-associated diseases: imaging findings, Eur. Radiol. 16 (2006) 459–468.

[4]  C.A. Helms, Fundamentals of Skeletal Radiology, second ed., Saunders, Philadelphia, 1995.

[5]  N.R. Kim, J.Y. Choi, S.H. Hong, et al., “MR corner sign”: value for predicting presence of ankylosing spondylitis, AJR Am. J. Roentgenol. 

191 (2008) 124–128.

[6]  J.A. Jacobson, G. Girish, Y. Jiang, B.J. Sabb, Radiographic evaluation of arthritis: degenerative joint disease and variations, Radiology 248 

(2008) 737–747.

[7]  C.C. Peterson, M.L. Silbiger, Reiter’s syndrome and psoriatic arthritis: their roentgen spectra and some interesting similarities, AJR Am. J. 

Roentgenol. 100 (1967) 860–871.

[8]  L.S. Steinbach, D. Resnick, Calcium pyrophosphate dihydrate crystal deposition disease revisited, Radiology 200 (1996) 1–9.

[9]  J.M. Taveras, J.T. Ferrucci, Radiology: Diagnosis, Imaging, Intervention, 2002 ed. on CD-ROM, Lippincott Williams & Wilkins, Philadelphia, 

2002.

Key Points: Differentiating Arthritis on Hand Radiograph

1.  Symmetric erosive change of the metacarpophalangeal and proximal interphalangeal joints of both hands, 

periarticular osteopenia, and symmetric joint space loss suggest RA.

2.  Extensive productive osteophyte changes of the distal interphalangeal joints, with less severe changes of the 

proximal interphalangeal and metacarpophalangeal joints, or a thickened “sausage-digit,” suggests psoriatic 

arthritis.

3.  Osteophyte production and joint space narrowing without marginal erosions of the distal interphalangeal and 

proximal interphalangeal joints, with little or no involvement of the metacarpophalangeal joints, suggests 

degenerative joint disease.

4.  A soft tissue mass with an overhanging rim of bone, adjacent to a joint space, suggests gout. Gout also tends 

to preserve the joint space and the mineralization of the bone.

5.  Calcifications within the soft tissues of the fingertips, resorption of the cortex of the finger tufts, or both suggest 

scleroderma or polymyositis.

Figure 40-4. 

CPDD with calcium crystal deposition in the meniscus 

(double arrows). This is called chondrocalcinosis.