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Arthritis overview


Introduction to arthritis

Classic Appearance of Arthritic Processes

  • When an arthritic process is well established in a particular patient, it will usually achieve a typical appearance, which allows diagnosis by means of imaging.
  • At such a moderately early or mid stage of disease, radiographs are usually sufficient to make the correct diagnosis.
  • The diagnosis usually depends on the location of the joint abnormalities and a host of other radiographic characteristics.


1. Location of involved joints

  • often eliminate some diagnoses and raise the probability of others.
  • For example, distal interphalangeal joint disease is commonly seen in psoriatic arthritis, osteoarthritis, and erosive osteoarthritis. However, it is not seen in rheumatoid arthritis until extremely late in the disease; thus RA should not be considered in an early arthritis.
  • Similarly, a disease involving the sacroiliac joints would raise the possibility of ankylosing spondylitis, inflammatory bowel disease arthritis, psoriatic spondyloarthropathy, chronic reactive arthritis, osteoarthritis, and DISH.
  • While the location of the joints involved certainly contributes to establishing a list of reasonable diagnoses, the lists can be relatively long, as in the examples above. There are several other parameters that are useful in honing that list to a single diagnosis that are outlined in the tables that follow.
  • Further explanation regarding some of these parameters may be helpful, as follows.


2. Age and gender

  • may be the easiest parameters to apply. There are a minimal number of arthritic processes that affect children (juvenile inflammatory arthritis, hemophilic arthropathy, inflammatory bowel disease arthropathy, and septic joint) and teenagers (in addition to those affecting children, early onset adult rheumatoid arthritis and ankylosing spondylitis).
  • Some diseases are gender specific (hemophilic arthropathy and hemochromatosis), while others are found in one gender far more frequently (gout, ankylosing spondylitis, chronic reactive arthritis in males, and rheumatoid arthritis in females).



3. character of the process

  • One of the most important parameters is the .
  • Some arthritides are purely erosive; rheumatoid arthritis is the hallmark for this group.
  • Others are purely bone-forming (also termed "productive"). This bone formation may appear in the form of osteophytes (as in osteoarthritis), enthesopathy or ligamentous ossification (as in ankylosing spondylitis, DISH, and OPLL), or periositis (as in psoriatic arthritis, chronic reactive arthritis, and juvenile idiopathic arthritis).
  • Other processes may be mixed, sometimes starting with erosions but progressing to osteophytes (as in pyrophosphate arthropathy or gout) or starting with periostitis and progressing to mixed erosions and osteophytes (as in psoriatic arthritis or chronic reactive arthritis). These processes tend to be distinctive for each type of arthritis by the time they are well established; between evaluating the character of the process and its primary location in an individual, the diagnosis can usually be secured.


4. Bilateral symmetry

  • of an arthritic process can be a useful characteristic.
  • Rheumatoid arthritis is especially well known for appearing bilaterally symmetric.
  • Note that rheumatologists do not require specific joints of specific digits to qualify the arthritis as symmetric. For example, 5th PIP left hand and 3rd PIP right hand would be considered symmetric disease simply because of PIP involvement of each hand.
  • Note also that bilateral symmetry may not be present in early stages of arthritic disease, even in rheumatoid arthritis.
  • Similarly, while we usually think of the sacroiliitis of ankylosing spondylitis as being bilaterally symmetric, in its early stages the symmetry is often strikingly absent. Therefore, useful generalizations regarding bilateral symmetry are most often made in the mature stages of the disease process. However, rigid application of "rules" of symmetry should be avoided when evaluating early arthritis.


5.Soft tissue swelling

  • can be the key to finding the earliest changes of arthritis on a radiograph.
  • The sausage digit may lead to the discovery of subtle periostitis, even in the absence of joint space narrowing or erosions.
  • Swelling around a metacarpophalangeal joint may lead to closer examination of a metacarpal head showing cortical indistinctness or the dot dash pattern of early inflammatory disease.
  • Be sure to window every image to evaluate the soft tissues, as these abnormalities can lead to closer examination of adjacent joints.


6.Soft tissue masses

  • are not frequently seen in conjunction with arthritic processes. However, they may lead to specificity in diagnosis.
  • Gouty tophi, seen as a mass containing a variable degree of dense tissue, can be diagnostic.
  • As another example, soft tissue nodules, combined with acroosteolysis and interphalangeal joint erosions, leads to the rare diagnosis of multicentric reticulohistiocytosis.
  • In differentiating between the ligamentous ossification of DISH/OPLL, osteophytes of spondylosis deformans, syndesmophytes of ankylosing spondylitis, and paravertebral ossification of psoriatic arthritis and chronic reactive arthritis, the character of paravertebral ossification can often suggest the correct diagnosis. However, as with other parameters, it is important to note that mature paravertebral ossification in each of these entities may all have a similar appearance.
  • True osteophytes may bridge across the disc space and give the appearance of the flowing ligamentous ossification of DISH. Mature ankylosing spondylitis has much bulkier syndesmophytes than the thin vertical ones depicted in early disease.


7. Subchondral cysts

  • are seen in virtually all arthritic processes and therefore are rarely useful in differentiating among them. However, occasionally the subchondral cysts are so large that this characteristic becomes useful in diagnosis.
  • Particularly large subchondral cysts in a setting that otherwise resembles rheumatoid arthritis lead to the diagnosis of robust rheumatoid arthritis.
  • Very large cysts are also noted in pyrophosphate arthropathy and pigmented villonodular synovitis.
  • Osteoarthritis and gout may also produce very large subchondral cysts.


8. Bone density

  • must always be interpreted within the context of patient age and gender.
  • An elderly female will usually have diffuse osteoporosis, with or without superimposed rheumatoid arthritis (classically described as causing juxtaarticular, followed by diffuse osteoporosis).
  • Thus, though we state that normal bone density is a characteristic of
  • osteoarthritis and gout, in an older patient those arthritic processes may be seen in the presence of diffuse osteoporosis.
  • Another example that may cause confusion is the young adult with end-stage renal disease and a renal transplant.
  • Erosive disease in these patients is likely to be gout or amyloid. However, the bone density will be decreased due to both their renal osteodystrophy and likely use of steroids for their transplant.
  • In this case, gout should be suggested to explain erosive disease, despite the bone appearing osteoporotic.
  • Focal osteoporosis can also be helpful in identifying joints with active inflammation, as the hyperemia from the inflammatory process leaches the calcium from the bone.


9. Pattern and timing of cartilage destruction

  • may be another useful parameter. Some arthritides, such as gout, classically cause prominent erosions before significant cartilage destruction, while most inflammatory arthritides, such as rheumatoid arthritis, result in early marginal erosions but also relatively early cartilage destruction.
  • The pattern of cartilage destruction also distinguishes the inflammatory arthropathies, where it is uniform throughout the joint as opposed to the more focal cartilage destruction seen in the weight-bearing portions of the joint in osteoarthritis.


10. Adjacent calcific or ossific densities

  • may be particularly helpful in diagnosis.
  • Chondrocalcinosis is not unique to pyrophosphate arthropathy but is most frequently seen in that disease.
  • The presence of chondrocalcinosis should also raise the question of traumatic osteoarthritis and hemochromatosis.
  • Calcifications in gouty tophi are usually unique in their appearance.
  • Calcific or ossific bodies in synovial chondromatosis are different from the osseous debris seen with a Charcot joint. Therefore, the character of adjacent
  • calcific or osseous densities may be useful in the diagnostic process.


11.Ankylosis of the peripheral joints

  • is most commonly seen in psoriatic arthritis and juvenile idiopathic arthritis.
  • It is commonly found in the spine of patients suffering from spondyloarthropathies (most frequently ankylosing spondylitis), DISH, and juvenile idiopathic arthritis.
  • Other more rare arthritic processes may show ankylosis as well.
  • On the other hand, ankylosis in cases of rheumatoid arthritis is exceedingly rare. Do not be fooled by a surgical arthrodesis in a patient with severe rheumatoid arthritis. Arthrodesis is often attempted to stabilize the digits in this disease, and may mimic ankylosis.

12.Early Appearance of Arthritic Processes

  • We are now diagnosing arthritic processes at an earlier stage, prior to any radiographic change.
  • This ability is essential, since early application of disease-modifying drug therapy may halt joint destruction.
  • The benefit of early diagnosis is obvious, yielding longer patient productivity and decreasing the need for arthroplasty. However, the diagnosis may be difficult with subtle or absent radiographic findings and relies on MR or ultrasound.
  • Early tenosynovitis and joint effusions may be identified on ultrasound, and MR may demonstrate tenosynovitis, effusion, and bone marrow edema long before actual erosions are seen in rheumatoid arthritis.
  • Inflammatory change at vertebral body corners may be identified on MR, indicating early spondyloarthropathy.
  • Even more subtle may be the enthesitis and adjacent marrow edema found in early ankylosing spondylitis, which are often found at the "corners" of the image (interspinous ligaments, iliac spine, greater trochanter) and are easily overlooked.
  • Close attention should be paid to these locations, even when evaluating a "routine lower back pain" spine MR exam.


13. Late Appearance of Arthritic Processes

  • End-stage arthritic processes may have a classic appearance.
  • Classic changes are often seen in the deformities and erosive change in rheumatoid patients or in the postural changes with vertebral column fusion in ankylosing spondylitis patients. However, at times an arthritic process, particularly when ineffectively treated, may attain a potentially confusing nonstandard appearance.
  • An example of this is the rheumatoid patient who has failed drug therapy, resulting in an arthritis mutilans appearance of the hands (remember that pencil-in-cup and arthritis mutilans are not exclusively seen in psoriatic arthritis).
  • Another example is the Native American ankylosing spondylitis patient who is treated without the use of Western medications and may present not only with the spondyloarthropathy expected in ankylosing spondylitis, but also with erosive disease involving all the peripheral joints, including hands and feet.
  • Finally, the classic disease process that may be confusing is end-stage gout, which, if misdiagnosed or undertreated, may result in spectacular erosive disease at unexpected locations.
  • It is important to remember that gout can look like anything and can be located at any joint!


14.Coexistence of Arthritic Processes

  • It is not unusual for two of the more common arthritic processes to coexist, particularly in the elderly patient.
  • This may be confusing initially but can be worked out through understanding the prevalence of the diseases in the patient population, as well as by paying attention to the appearance and location of the abnormalities present.
  • The most common combination is a new onset of rheumatoid arthritis superimposed on osteoarthritis.
  • In this case, the osteoarthritis is usually well-established, involving the 1st carpometacarpal and interphalangeal joints in classic fashion, but there is new
  • inflammatory change seen in the metacarpophalangeal joints.
  • The elderly patient may also develop pyrophosphate arthropathy, superimposed over osteoarthritis or rheumatoid arthritis.
  • The patient with a diabetic Charcot joint may develop superimposed septic arthritis.
  • Keeping these possibilities in mind is useful to the interpreter, as the pattern of disease may not be classic.

(common: Red; less common: Yellow)



Rheumatoid arthritis


RA distribution  is shown. The hand is the hallmark of the disease, with distal radioulnar joint, radiocarpal joint, intercarpal joint, MCP & PIP joint involvement. Retrocalcaneal and 5th MTP involvement is most common in the foot, with other ankle/hindfoot joints involved less commonly. Hip, knee, shoulder, elbow, temporomandibular, and

cervical involvement are common as well.


Juvenile rheumatoid arthritis


JIA distribution is shown. The knee, ankle, and elbow are most frequently involved. In the hand, pericapitate and proximal interphalangeal joints are most frequent, followed by radiocarpal, carpometacarpal, and metacarpophalangeal joints. Cervical spine and temporomandibular involvement are common, while the shoulder and hip are less so.



OA distribution  is shown. Hands show common involvement of the 1st carpometacarpal and scapho-trapeziotrapezoid joints, as well as the distal interphalangeal joints. Foot involvement is most frequent at the 1st metatarsophalangeal joint, with the ankle, subtalar, talonavicular, and tarsometatarsal joints less frequently involved. Hip and knee OA are common, while shoulder and elbow are less common. All elements of the spine are commonly affected.

Primary synovial chondromatosis

PSC distribution is shown. Knee involvement is most common, followed by elbow, shoulder, and hip. Axial involvement is virtually never seen. The rare process tenosynovial chondromatosis affects the hands and feet.


Diffuse idiopathic skeletal hyperostosis

DISH and ossification of posterior longitudinal ligament (OPLL) distribution  are shown. These processes are shown

together since they have considerable overlap in distribution, with OPLL predominating in the cervical spine and DISH predominating in the thoracic spine. The nonsynovial portions of the sacroiliac joints (upper 1/2 to 2/3) are affected in DISH.




Ankylosing spondylitis


AS & inflammatory bowel disease spondyloarthropathy (IBD) distribution are shown. These are shown together; their distribution is identical. All elements of the spine may be involved, along with the sacroiliac joints and large proximal joints (hips, shoulders, and less commonly, knees). With advanced disease, the wrist and ankles may be affected.



Psoriatic arthritis

PSA distribution is shown. The Spondyloarthropathy involves all the elements of the spine as well as the

sacroiliac joints. The hands show the most frequent peripheral joint involvement, especially in the pericapitate and IP joints. Less frequently, the lower extremities may be involved (foot, ankle, knee, hip).


Chronic reactive arthritis


CRA distribution is shown. The Spondyloarthropathy involves all the elements of the spine as well as the sacroiliac joints. This axial distribution is identical to that of psoriatic arthritis. The feet show the most frequent peripheral joint involvement, with the retrocalcaneal, hindfoot, midfoot, and forefoot all at risk. Knee involvement is also seen. Hand and wrist involvement is considerably less frequent, seen either in advanced disease or sporadically



Gout distribution  is shown. Involvement of the 1st MTP joint is the hallmark of the disease, though other foot & ankle joints may be affected. In the hand, the IP joints are much more frequently affected than the MCP or carpals. Of the more proximal joints, the elbow is more frequently involved than the knee. Axial involvement of the C spine &  SI joints is uncommonly seen.




Pyrophosphate Arthropathy

Pyrophosphate arthropathy distribution is shown. The wrist shows a specific predilection for radiocarpal involvement, often leading to SLAC deformity, while the MCP joints are affected in the hand (2nd & 3rd earlier and more frequently than 4th & 5th). The knee is commonly involved, as are the hips & symphysis pubis. The upper elements of the C spine are often affected as well.





Hemochromatosis distribution. Disease affecting the wrist shows a distinct predilection for the radiocarpal joint. In the hand, the metacarpophalangeal joints are distinctively involved; the 2nd and 3rd are found to be abnormal both earlier and more severely than the 1st, 4th, and 5th. Note that this distribution is similar to that of pyrophosphate arthropathy in the wrist and hand. The remainder of the skeleton is only rarely affected.





Amyloid distribution. The large proximal joints (shoulder, hip, and knee) are particularly prone to involvement. In the hand, any joint may be involved, but the interphalangeal joints and radiocarpal joints are more frequently abnormal. Ankle and foot interphalangeal joints may be affected as well..

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