Note: This copy is for your personal non-commercial use only. To order presentation-ready copies for distribution to your colleagues or clients, contact us at www.rsna.org/rsnarights. Radiographic Evaluation of Arthritis: Inflammatory Conditions1 REVIEW FOR RESIDENTS Ⅲ Jon A. Jacobson, MD In the presence of joint space narrowing, it is important to Gandikota Girish, MD differentiate inflammatory from degenerative conditions. Yebin Jiang, MD, PhD Joint inflammation is characterized by bone erosions, os- Donald Resnick, MD teopenia, soft-tissue swelling, and uniform joint space loss. Inflammation of a single joint should raise concern for infection. Multiple joint inflammation in a proximal distri- REVIEWS AND COMMENTARY bution in the hands or feet without bone proliferation suggests rheumatoid arthritis. Multiple joint inflammation in a distal distribution in the hands or feet with bone proliferation suggests a seronegative spondyloarthropa- thy, such as psoriatic arthritis, reactive arthritis, or anky- losing spondylitis. ௠ RSNA, 2008 1 From the Department of Radiology, University of Michi- gan Medical Center, 1500 E Medical Center Dr, TC- 2910L, Ann Arbor, MI 48109-0326 (J.A.J., G.G., Y.J.); and Department of Radiology, University of California San Diego VA Hospital, La Jolla, Calif (D.R.). Received Decem- ber 11, 2006; revision requested February 7, 2007; revi- sion received July 25; accepted August 20; final version accepted November 1; final review by J.A.J. Address correspondence to J.A.J. (e-mail: [email protected] ). ஽ RSNA, 2008 378 Radiology: Volume 248: Number 2—August 2008 REVIEW FOR RESIDENTS: Radiographic Evaluation of Arthritis Jacobson et al adiography is typically the first algorithm does not include substantial features of a degenerative joint, as well. imaging study in evaluation for ar- detail of each topic but rather focuses In addition to lack of the findings de- Rthritis. On radiographs, one criti- on radiographic findings that, with the scribed for inflammatory joint disease, cal assessment is differentiating inflam- use of this algorithm, lead to a final and degenerative findings include osteo- matory arthritis from a degenerative usually correct diagnosis. The first criti- phyte formation and bone sclerosis process, because the treatment options cal step in the algorithm is to determine (Fig 4). Although underlying cartilage are quite different. Identification of an if joint space narrowing detected with damage is presumed, joint space nar- inflammatory joint due to infection often radiography is related to an inflamma- rowing does not involve the joint uni- requires diagnostic aspiration followed tory or a degenerative condition. formly, as is seen with inflammatory by administration of antibiotics and pos- joint disease, and osteophytes are typi- sible surgical drainage and lavage. With cally present. As the joint space nar- regard to systemic arthritides, with Inflammatory versus Degenerative rows, the osteophytes become larger, early diagnosis there are several types Joint Disease sclerosis increases, and subchondral of medications used to control joint in- There exist essential radiographic find- cysts—or geodes—may be seen. If de- flammation and even prevent or reduce ings that are common to inflammatory generative joint disease involves a syno- subsequent joint destruction. The treat- arthritis due to any cause. The hallmark vial articulation, the term osteoarthro- ment options for a degenerative process of joint inflammation is erosion of bone. sis or osteoarthritis is appropriate. include medication, joint injection, and, This will initially appear as a focal dis- later, joint replacement. continuity of the thin, white, subchon- The objective of this review is to dral bone plate (Fig 2). Normally, this Inflammatory Arthritis present a simplified approach to radio- subchondral bone plate can be seen graphic evaluation of arthritis (Fig 1). even in cases of severe osteopenia, Septic Arthritis This is presented as an algorithm that whereas its discontinuity indicates ero- Once joint space narrowing and fea- uses joint space narrowing of the distal sion. Although it is true that periarticu- tures of inflammatory arthritis are iden- extremities as a starting point. While it lar osteopenia and focal subchondral os- tified, the next step in the algorithm is to is acknowledged that it is nearly impos- teopenia can appear prior to a true determine how many joints are in- sible to include all types of arthritis in bone erosion, it is the presence of bone volved. Multiple joints may be involved one simple algorithm, and that there are erosion that indicates definite joint in- in as many as 20% of cases (1). If joint always exceptions and variations, this flammation. As the bone erosion en- inflammation is limited to a single joint, approach will encompass the most com- larges, osseous destruction extends into infection must first be carefully ex- mon features of the frequently seen ar- the trabeculae within the medullary cluded (Fig 1). The cause of septic ar- thritides and can be viewed as a frame- space. thritis is usually related to hematoge- work for radiographic evaluation. This One important feature of inflamma- nous seeding owing to staphylococcal or tory arthritis relates to the concept of a streptococcal microorganisms. marginal bone erosion. This term is The radiographic features of a sep- Essentials given to bone erosion that is located at tic joint encompass those of any inflam- Ⅲ It is important to differentiate in- the margins of an inflamed synovial matory arthritis—namely, periarticular flammatory from degenerative joint. This specific location represents osteopenia, uniform joint space narrow- causes of joint space narrowing. that portion of the joint that is intraar- ing, soft-tissue swelling, and bone ero- Ⅲ Inflammatory arthritis is charac- ticular but not covered by hyaline carti- sions (Fig 5). Not all findings may be terized by bone erosions, osteope- lage; therefore, early joint inflammation present simultaneously, and, acutely, nia, soft-tissue swelling, and uni- will produce marginal erosions prior to bone erosions may not be evident. Fur- form joint space narrowing. erosions of the subchondral bone plate thermore, the joint space may be ini- Ⅲ With monoarticular joint inflam- beneath the articular surface (Fig 3). tially widened owing to the effusion. mation, it is important to exclude When looking for bone erosions, multi- Joint space widening may also be seen infection. ple views of a joint are essential to pro- with more indolent and atypical infec- Ⅲ Inflammation that involves multi- file the various bone surfaces. tions, such as those related to tubercu- ple joints in a proximal distribu- A second important characteristic losis and fungal agents; but, again, other tion of the hands or feet without of an inflammatory joint process is uni- inflammatory changes are typically present bone proliferation suggests rheu- form joint space narrowing. This occurs matoid arthritis. because destruction of the articular car- Ⅲ Inflammation that involves multi- tilage is uniform throughout the intraar- Published online ples joints in a distal distribution ticular space. A third finding of inflam- 10.1148/radiol.2482062110 of the hands or feet with bone matory joint disease is soft-tissue swell- Radiology 2008; 248:378–389 proliferation suggests a seronega- ing. tive spondyloarthropathy. There are essential radiographic Authors stated no financial relationship to disclose. Radiology: Volume 248: Number 2—August 2008 379 REVIEW FOR RESIDENTS: Radiographic Evaluation of Arthritis Jacobson et al (Fig 6). The Phemister triad describes to identify cortical discontinuity. If a In the feet, target sites of rheuma- these findings classically seen in tuber- round subchondral lucency does not toid arthritis include the metatarsopha- culous arthritis: juxtaarticular osteope- interrupt the bone surface, possibili- langeal, proximal interphalangeal (in- nia, peripheral bone erosions, and grad- ties include a subchondral cyst or an cluding the first interphalangeal), and ual narrowing of the joint space (2). erosion viewed en face. intertarsal joints, and such involvement Rheumatoid Arthritis Figure 1 If joint space narrowing and other ra- diographic findings of inflammatory ar- thritis involve multiple joints, a systemic arthritis must be considered. The next step in the algorithm is evaluation of the hands and feet. Proximal distribution at these sites and lack of bone prolifera- tion suggest the diagnosis of rheumatoid arthritis. Rheumatoid arthritis is most common in women aged 30–60 years. Serologic markers such as rheumatoid factor and antibodies to cyclic citrulli- nated peptide are important indicators of rheumatoid arthritis (3,4). The radiographic features of rheu- matoid arthritis are those of joint in- flammation and include periarticular osteopenia, uniform joint space loss, bone erosions, and soft-tissue swelling (Fig 7). Because of the chronic nature of the inflammation, additional findings Figure 1: Flow chart shows approach to radiographic evaluation of arthritis. Algorithm begins with joint such as joint subluxation and subchon- space narrowing and initially uses differentiation between inflammatory and degenerative findings to reach the dral cysts may also be evident. Although final diagnosis. the radiographic findings are not spe- cific for one condition, the proximal dis- tribution of joint involvement in the Figure 2 hands and feet and the lack of bone proliferation suggest rheumatoid arthri- tis. In the hands, target sites of rheu-