Inflammatory Arthritides
The inflammatory arthritides constitute a group of diverse monoarticular and systemic disorders that have in common one important feature: inflammatory pannus eroding articular cartilage and bone (Fig. 6.1). An overview of the clinical and imaging hallmarks of the various inflammatory arthritides is shown in Table 6.1.
EROSIVE OSTEOARTHRITIS (EOA)
Erosive osteoarthritis was first described by Kellgren and Moore in 1952 and reintroduced in 1961 by Crain, who called it interphalangeal osteoarthritis. He defined this disorder as a localized variant of osteoarthritis involving the finger joints, characterized by degenerative changes with intermittent inflammatory episodes leading to deformities and ankylosis. In 1966, Peter and Pearson coined the term erosive osteoarthritis, and Ehrlich in 1972 described it as inflammatory osteoarthritis, based on the clinical symptoms of swelling, tenderness, erythema, warmth, and limitation of function. It can be defined as a progressive disorder of the interphalangeal joints with severe synovitis, superimposed on the changes of degenerative joint disease. Although the cause is still unclear, several investigators have suggested hormonal influences, metabolic background, autoimmunity, and heredity as being involved.
Clinical Features
EOA is a progressive inflammatory arthritis seen predominantly in middle-aged women. Only rarely are men affected, with an estimated female-to-male ratio of 12:1. Patients’ ages range from 36 to 83 years, and mean age of onset is 50.5 years. This condition combines certain clinical manifestations of rheumatoid arthritis with certain imaging features of degenerative joint disease. Generally, involvement is limited to the hands, with the proximal and distal interphalangeal joints being the most commonly affected. Large joints, such as the hip or shoulder, are only rarely involved. The arthritis usually begins abruptly and is characterized by pain, swelling, and tenderness of the small joints of the hands. Also described are throbbing paresthesias of the fingertips and morning stiffness.
Pathology
Proliferative synovitis is the most common histopathologic feature of EOA and cannot be distinguished from that of seen in rheumatoid arthritis. Moreover, Peter et al. described findings in some patients consisting of degenerative cartilage with prominent subchondral granulation tissue, lymphocyte aggregates, plasma cell infiltration, and subsynovial fibrosis. Loose fibrin-like material was noted interstitially as well as villous hypertrophy, hyperemia and thickening of the blood vessel walls, and organizing amorphous exudates that overlaid the synovium. Generally speaking, the pathologic synovium of EOA exhibits features that are consistent with both RA and OA.
Imaging Features
In the early stage of the disease, the main feature is symmetric synovitis of the interphalangeal joints. Later, this is followed by articular erosions, which exhibit a characteristic radiographic feature named the “gull-wing” deformity by Martel. This configuration is seen as a result of central erosion and marginal proliferation of bone (Figs. 6.2 and 6.3); Heberden nodes may also be present. Periosteal reaction taking the form of linear or fluffy bone apposition over the cortex near the affected joints is occasionally
observed. Swelling of soft tissue, usually fusiform, may be present around involved articulations (see Figs. 6.2A and 6.3E, F); however, periarticular osteoporosis is rarely present. Later in the disease process, bone ankylosis of the phalanges may develop (see Fig. 6.3G). Approximately 15% of patients with erosive osteoarthritis may have clinical, laboratory, and imaging manifestations of rheumatoid arthritis (Fig. 6.4). The exact relationship between these two conditions is still unclear. Some investigators believe that erosive osteoarthritis is actually rheumatoid arthritis originating in unusual sites but subsequently progressing to the articulations that are more typically involved. Others suggest that each is a distinct entity, citing as evidence the fact that the synovial fluid of patients with rheumatoid arthritis does not resemble that of patients with erosive osteoarthritis, that the immunologic abnormalities commonly seen in rheumatoid arthritis are absent in the latter condition, and that the serologic test for rheumatoid factor is negative.
observed. Swelling of soft tissue, usually fusiform, may be present around involved articulations (see Figs. 6.2A and 6.3E, F); however, periarticular osteoporosis is rarely present. Later in the disease process, bone ankylosis of the phalanges may develop (see Fig. 6.3G). Approximately 15% of patients with erosive osteoarthritis may have clinical, laboratory, and imaging manifestations of rheumatoid arthritis (Fig. 6.4). The exact relationship between these two conditions is still unclear. Some investigators believe that erosive osteoarthritis is actually rheumatoid arthritis originating in unusual sites but subsequently progressing to the articulations that are more typically involved. Others suggest that each is a distinct entity, citing as evidence the fact that the synovial fluid of patients with rheumatoid arthritis does not resemble that of patients with erosive osteoarthritis, that the immunologic abnormalities commonly seen in rheumatoid arthritis are absent in the latter condition, and that the serologic test for rheumatoid factor is negative.
 Figure 6.1 ▪ Inflammatory arthritides. Highlights of the morphology and distribution of arthritic lesions in the inflammatory arthritides. |
Table 6.1 CLINICAL AND IMAGING HALLMARKS OF INFLAMMATORY ARTHRITIDES | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Because imaging presentation of erosive and nonerosive osteoarthritis may be similar, the investigators were looking into the other means to distinguish these two conditions. The recent studies of serum biomarkers were very promising in this respect. They demonstrated elevation of myeloperoxidase,
C-reactive protein, and serum levels of nitrated form of a marker of type II collagen denaturation (Coll2-1NO2) in patients with EOA.
C-reactive protein, and serum levels of nitrated form of a marker of type II collagen denaturation (Coll2-1NO2) in patients with EOA.
 Figure 6.2 ▪ Erosive osteoarthritis. A: Dorsovolar radiograph of the fingers of both hands of a 51-year-old woman shows characteristic gull-wing erosions of several proximal and distal interphalangeal joints, a configuration resulting from peripheral bone erosion in the distal side of the joint and central erosion in the proximal side of the joint, associated with marginal bone proliferation. Note also accompanied fusiform soft tissue swelling. B: Radiograph of the fingers of both hands of a 49-year-old woman shows typical erosions affecting proximal interphalangeal joint of the middle finger of the right hand and distal interphalangeal joints of both hands. C: Dorsovolar radiograph of the left hand of a 48-year-old woman shows the typical involvement of the proximal and distal interphalangeal joints exhibiting gull-wing pattern. |
Differential Diagnosis
The conditions to be considered in differential diagnosis of EOA include primarily classic interphalangeal osteoarthritis, rheumatoid arthritis, and psoriatic arthritis. In interphalangeal OA, certain features, including osteophytosis, subchondral sclerosis, narrowing of the joint spaces, and Heberden and Bouchard nodes, are similar to those of EOA. However, joint erosions and interphalangeal ankylosis are absent. The relationship of EOA to OA and RA still remains a matter of controversy. Some investigators regard EOA as an entirely separate entity, whereas others believe that it represents the end spectrum of OA or perhaps an interface between OA and RA. Ehrlich noted the superimposition of clinical, laboratory, and imaging features of RA in 62 of 170 patients (15%) whose initial diagnosis was EOA. He was first to suggest a relationship between EOA and RA. Conversely, Martel and associates hypothesize that erosions in EOA reflect the intensity and duration of inflammation, favoring the OA spectrum of the disease rather than separate disease entities. The distribution of affected joints in OA and EOA in the hand is identical, with a distinct propensity for DIP and PIP joints as well occasional involvement of the first carpometacarpal and metacarpophalangeal articulations. However, in classic OA affecting the hand, the articular erosions are absent. In addition, Smith and coworkers in their research study of OA and EOA observed that patients with EOA exhibited more severe imaging features of OA in those joints with erosive changes than in the joints without such changes. It is worthwhile to indicate that in adult onset of RA, unlike in EOA, the distal interphalangeal joints are commonly spared, and the erosions are marginal rather than central. In juvenile onset of RA (juvenile idiopathic arthritis), however, the DIP joints may also be affected. Both forms of RA are characterized by notable periarticular osteoporosis, which usually is absent in EOA. There are also differences in the clinical and laboratory findings. Latex agglutination tests for rheumatoid factor are typically negative, the ESR is normal or only minimally elevated, and the synovial fluid reveals no significant inflammatory changes. Moreover, patients do not experience prolonged morning stiffness. Subcutaneous nodules, a common clinical feature of RA, are absent, and no subluxation or dislocation is observed in the interphalangeal joints.
Another condition to be distinguished from EOA is psoriatic arthritis. Both arthritides preferentially affect the DIP joints, but the erosions of psoriatic arthritis are usually marginally located, similar to those of RA. Unlike EOA, which almost invariably has a symmetric distribution, most patients with psoriatic arthritis exhibit asymmetrical
joint involvement. Moreover, PA is characterized by other abnormalities not seen in EOA, including skin lesions, nails abnormalities, involvement of sacroiliac joints (sacroiliitis), paraspinal ossifications, and formation of broad-based osteophytes at the plantar aspect of the calcaneus, accompanied by fluffy periostitis. Fluffy periostitis is also seen in the short tubular bones, unlike linear bone apposition observed in EOA. The articular erosions at the DIP joints are also different, with “mouse-ear” rather than “gull-wing” configuration. Lastly, acro-osteolysis and tapered erosions with pencil-like deformities, leading to the so-called arthritis mutilans, are absent in EOA. Although osteophytosis is a consistent phenomenon in EOA, it is almost never seen in RA or PA. When it accompanies the latter conditions, it is secondary because of superimposed degenerative changes rather than a primary feature.
joint involvement. Moreover, PA is characterized by other abnormalities not seen in EOA, including skin lesions, nails abnormalities, involvement of sacroiliac joints (sacroiliitis), paraspinal ossifications, and formation of broad-based osteophytes at the plantar aspect of the calcaneus, accompanied by fluffy periostitis. Fluffy periostitis is also seen in the short tubular bones, unlike linear bone apposition observed in EOA. The articular erosions at the DIP joints are also different, with “mouse-ear” rather than “gull-wing” configuration. Lastly, acro-osteolysis and tapered erosions with pencil-like deformities, leading to the so-called arthritis mutilans, are absent in EOA. Although osteophytosis is a consistent phenomenon in EOA, it is almost never seen in RA or PA. When it accompanies the latter conditions, it is secondary because of superimposed degenerative changes rather than a primary feature.
 Figure 6.3 ▪ Erosive osteoarthritis. A: Cone-down view of the index, middle, and ring fingers of a 70-year-old man shows gull-wing erosions of the distal interphalangeal joints. B: Cone-down view of the middle and ring fingers of a 66-year-old woman shows advanced erosions of the proximal interphalangeal joints and early erosions of the distal interphalangeal joints. C: Cone-down view shows characteristic erosion of the proximal interphalangeal joint of the ring finger and distal interphalangeal joint of the index finger of a 53-year-old woman. D: Radiograph of the index and middle fingers of a 50-year-old woman shows gull-wing erosions of the distal interphalangeal joints. |
 Figure 6.3 ▪ (Continued) E: Dorsovolar radiograph of the left thumb of a 51-year-old woman shows characteristic gull-wing erosion of the interphalangeal joint. Note adjacent fusiform soft tissue swelling and lack of periarticular osteoporosis. F: In another patient, a 50-year-old woman, gull-wing erosion is accompanied by periosteal reaction and fusiform soft tissue swelling, very similar to psoriatic arthritis. G: In this patient, a 69-year-old woman, apart from the typical erosions of the proximal interphalangeal joint of the middle finger and distal interphalangeal joint of the index finger, observe also the fusion of the distal interphalangeal joints of the middle and ring fingers. |
Very rarely, erosive changes in the interphalangeal joints seen in hyperparathyroidism arthropathy can simulate
those present in EOA. However, differential features include osteopenia, invariably accompanying the changes of hyperparathyroidism, and frequent occurrence of acroosteolysis, a hallmark of former condition. Moreover, the erosions seen in hyperparathyroidism arthropathy are not as sharply demarcated as in EOA, being the result of periosteal, chondral, and subchondral resorption. Other features of hyperparathyroidism, including cortical “tunneling,” “brown” tumors, soft tissue calcifications, and involvement of ligaments and tendons leading to joint laxity and instability, are additional differentiating features.
those present in EOA. However, differential features include osteopenia, invariably accompanying the changes of hyperparathyroidism, and frequent occurrence of acroosteolysis, a hallmark of former condition. Moreover, the erosions seen in hyperparathyroidism arthropathy are not as sharply demarcated as in EOA, being the result of periosteal, chondral, and subchondral resorption. Other features of hyperparathyroidism, including cortical “tunneling,” “brown” tumors, soft tissue calcifications, and involvement of ligaments and tendons leading to joint laxity and instability, are additional differentiating features.
 Figure 6.4 ▪ Progression of erosive osteoarthritis into rheumatoid arthritis. A: Dorsovolar radiograph of the hand of a 58-year-old woman demonstrates the gull-wing configuration of erosive changes in the proximal interphalangeal joints and the distal interphalangeal joint of the small finger. Because of protracted pain and lack of response to conservative treatment, she underwent joint resection followed by implantation of silicone-rubber prostheses in the proximal interphalangeal joints of the index, middle, and ring fingers, together with fusion of the interphalangeal joint of the thumb and the distal interphalangeal joint of the small finger. Five years after surgery, the classic radiographic features of rheumatoid arthritis developed, involving the wrists (B), elbows, shoulders, hips, and cervical spine. Note the surgical fusion of interphalangeal joints of the thumb and fifth finger, as well as the spontaneous fusion of the distal interphalangeal joints of the index and ring fingers. |
Occasionally, a variant of erosive osteoarthritis may be seen as one of the features of Cronkhite-Canada syndrome. This rare systemic disorder also manifests with generalized gastrointestinal polyposis, hyperpigmentation of the skin, and nail atrophy.
Treatment
The main objective of therapy in patients with inflammatory erosive osteoarthritis is relief of pain and restoration of joint function. Nonpharmacologic therapy includes physical and occupational therapy. Range-of-motion exercises and moist heat, in the form of a paraffin bath, are helpful. Pharmacologic methods include analgesics, nonsteroidal anti-inflammatory drugs (NSAIDs), and corticosteroids. Selected cases have also been treated in the past with methotrexate and oral gold salts. Recently, promising results have been achieved with administration of hydroxychloroquine in patients who did not respond to NSAIDs. Also good results have been reported after subcutaneous injections of adalimumab and intra-articular injections of infliximab. Surgical intervention is often necessary for the relief of persistent pain and the correction of severe deformities. One of the most effective procedures is joint replacement by means of silicone-rubber arthroplasties (see Fig. 6.4B). The indications for this type of surgery are loss of the joint space, synovial proliferation with joint destruction, loss of normal alignment, and uncontrollable pain.
RHEUMATOID ARTHRITIS (RA)
Rheumatoid arthritis is a progressive, chronic, systemic inflammatory disease affecting primarily the synovial joints, leading to synovial inflammation and proliferation, loss of articular cartilage, and erosions of subchondral bone. The pathophysiologic hallmark of this condition is formation of pannus, which refers to hypertrophied synovium that develops as inflammatory response. The destructive action of pannus is responsible for progressive erosions and joint surface damage and ligament and joint capsule tearing, all leading to joint deformities and instability. Women are affected three times more often than are men. The course of the disease varies from patient to patient, and there is a striking tendency toward spontaneous remissions and exacerbations.
Although it is much enigmatic, most rheumatologists also include under the rubric of “rheumatoid arthritis” a condition called seronegative rheumatoid arthritis (see text below), in which patients present without rheumatoid factor or antibodies to CCP but with the clinical and imaging picture of rheumatoid arthritis. Currently, rheumatoid arthritis is considered to be a heterogeneous autoimmune disorder, with genetic factors playing an important role in the disease expression. Multiple genome-wide association studies have been conducted, but the results have generally been disappointing. The genetics is complex and multifactorial and varies between ethnic populations. The best association is with the major histocompatibility complex (MHC), but the data have yielded no practical clues that can be translated to the bedside. Although the association with the susceptibility loci of HLA-DRB1 (which encodes the β-chain of HLA-DR) and PTPN22 genes is better understood, several non-HLA loci have been linked to this arthritis, including the 18q21 chromosome region of the TNFRSR11A gene, which encodes the receptor activator of nuclear factor kappaB. In addition, a common genetic variant at the TRAF1-C5 locus on chromosome 9 is associated with an increased risk of anti-CCP-positive rheumatoid arthritis. Allelic variants of HLA-DRB1 associated with risk for rheumatoid arthritis encode a similar sequence, namely, amino acids 70 to 74, known as the shared epitope (SE). The detection of antibodies to citrullinated proteins (CCP), representing specific autoantibodies in the patient’s serum, is an important diagnostic finding.
Although it is much enigmatic, most rheumatologists also include under the rubric of “rheumatoid arthritis” a condition called seronegative rheumatoid arthritis (see text below), in which patients present without rheumatoid factor or antibodies to CCP but with the clinical and imaging picture of rheumatoid arthritis. Currently, rheumatoid arthritis is considered to be a heterogeneous autoimmune disorder, with genetic factors playing an important role in the disease expression. Multiple genome-wide association studies have been conducted, but the results have generally been disappointing. The genetics is complex and multifactorial and varies between ethnic populations. The best association is with the major histocompatibility complex (MHC), but the data have yielded no practical clues that can be translated to the bedside. Although the association with the susceptibility loci of HLA-DRB1 (which encodes the β-chain of HLA-DR) and PTPN22 genes is better understood, several non-HLA loci have been linked to this arthritis, including the 18q21 chromosome region of the TNFRSR11A gene, which encodes the receptor activator of nuclear factor kappaB. In addition, a common genetic variant at the TRAF1-C5 locus on chromosome 9 is associated with an increased risk of anti-CCP-positive rheumatoid arthritis. Allelic variants of HLA-DRB1 associated with risk for rheumatoid arthritis encode a similar sequence, namely, amino acids 70 to 74, known as the shared epitope (SE). The detection of antibodies to citrullinated proteins (CCP), representing specific autoantibodies in the patient’s serum, is an important diagnostic finding.
In 2010, the American College of Rheumatology in collaboration with European League Against Rheumatism established new classification criteria for rheumatoid arthritis (RA). Their work “focused on identifying, among patients newly presenting with undifferentiated inflammatory synovitis, factors that best discriminated between those who were and those who were not at high risk for persistent and/or erosive disease—this being the appropriate current paradigm underlying the disease construct ‘rheumatoid arthritis.’” The main advantage of this new classification is focusing on features at earlier stages of rheumatoid arthritis rather than defining the disease by its late-stage features, as it was practiced in the past. In the established new criteria, classification as “definite RA” was based on the presence of synovitis in at least one joint, absence of alternative diagnosis that better explains the synovitis, and achievement of a total score of 6 or greater (out of possible 10) from the individual scores in four categories: number and site of involved joints (score range from 0 to 5), serologic abnormality (score range from 0 to 3), elevated acute-phase response (score range from 0 to 1), and duration of symptoms (two levels; range from 0 to 1).
Serology of Rheumatoid Arthritis
Rheumatoid factors, so widely used by clinicians, are anti-gamma globulin antibodies that are generally IgM and combine with their antigens (immunoglobulin G [IgG]) to form immune complexes. These complexes activate the complement system, which releases mediators responsible for producing inflammation within the joint structures. Because rheumatoid factors can be found in the serum and in joint fluids of patients with nonrheumatoid disorders, their presence alone is not diagnostic of rheumatoid arthritis. They have been studied for decades and were once thought to be the only critical serologic marker of rheumatoid arthritis; this, however, is not the case, because rheumatoid factors can be found in the joint fluid of patients with nonrheumatoid disorders. Although the rheumatoid factor is still widely used, it has lost much of the luster of the past. Nevertheless, finding high titers of these factors in a joint effusion strongly suggests the diagnosis of rheumatoid arthritis. Early in the course of disease, rheumatoid factors may be demonstrated in the synovial fluid before they are positive in the serum, allowing early diagnosis. Rheumatoid factors do participate in the pathogenesis of rheumatoid arthritis through the formation of local and circulating antigen-antibody complexes. In synovial fluid, IgM and IgG rheumatoid factors can combine to form immune complexes. The complement system is activated, resulting in the attraction of polymorphonuclear leukocytes into the joint space. Discharge of their hydrolytic enzymes causes the destruction of joint tissues. The process initiating these events is as yet unknown. Patients with rheumatoid arthritis with subcutaneous nodules almost always will have positive rheumatoid factors, generally in high titer. Interesting, however, is the fact that frequency and severity of rheumatoid nodules has greatly deceased in population and the disease is strikingly different in this respect from two generations ago.
As already discussed in the text above, autoantibodies against the group of citrullinated proteins (CCPs) are more pathognomonic for rheumatoid arthritis than rheumatoid factors. The second-generation enzyme-linked immunosorbent assay (ELISA) tests for anti-cyclic citrullinated peptide 2 (anti-CCP2) antibodies have specificity for RA as high as 97%. These antibodies are directed at one or all of the following proteins: alpha enolase, fibrinogen, and vimentin. In all cases, the arginine in these proteins has been replaced by the plant amino acid citrulline. In people with a genetic predisposition to loss of tolerance, autoantibodies to these CCPs appear and may be detected many years before the clinical onset of rheumatoid arthritis. There are several factors known to accelerate this loss of tolerance, including smoking and infections, particularly Proteus infections of the gums.
Clinical Features
Articular and periarticular manifestations include joint swelling and tenderness to palpation, with morning stiffness and severe motion impairment in the affected joints. The clinical presentation varies between the patients, but an insidious onset of pain with symmetrical swelling of the joints of the hands is the most common finding. Some patients may present with palindromic onset, monoarticular presentation, extra-articular synovitis (such as tenosynovitis and bursitis), and general symptoms such as malaise, fatigue, anorexia, weight loss, and low-grade fever.
Imaging Features
Rheumatoid arthritis is characterized by a diffuse, usually multicompartmental, symmetric narrowing of the joint space associated with marginal or central erosions, periarticular osteoporosis, and periarticular soft tissue swelling; subchondral sclerosis is minimal or absent and formation of osteophytes is lacking.
Large Joint Involvement
Any of the large weight-bearing and non-weight-bearing joints can be affected by rheumatoid arthritis. Regardless of the size of the joint and the site of involvement, certain imaging features can be identified that are characteristic of this inflammatory process.
 Figure 6.5 ▪ Rheumatoid arthritis of the hip joints. A: Anteroposterior radiograph of the pelvis of a 47-year-old woman shows uniform narrowing of both hip joints accompanied by axial migration of the femoral heads. B: Anteroposterior radiograph of the right hip of a 60-year-old woman with advanced rheumatoid arthritis shows concentric joint space narrowing, with axial migration of the femoral head leading to acetabular protrusion. Some superimposed secondary osteoarthritic changes are also present. C: Anteroposterior radiograph of the left hip of a 64-year-old woman shows erosions of the femoral head and acetabulum, concentric narrowing of the hip joint, and acetabular protrusion. |
Osteoporosis
In rheumatoid arthritis, unlike osteoarthritis, osteoporosis is a striking feature. In the early stage of the disease, osteoporosis is localized to periarticular areas (juxta-articular osteoporosis), but with progression of the condition, a generalized osteoporosis can be observed.
Joint Space Narrowing
This is usually a symmetric process with concentric narrowing of the joint. Concentric narrowing in the hip joint leads to axial migration of the femoral head, which in more advanced stages may result in acetabular protrusio (Figs. 6.5 and 6.6). Similar concentric joint space narrowing is observed in the shoulder joint (Fig. 6.7). In
addition, cephalad migration of the humeral head may be seen secondary to destructive changes in the shoulder joint and rupture of the rotator cuff (Fig. 6.8A); resorption of the distal end of the clavicle, which assumes a pencil-like appearance, may also be observed. Tear of the rotator cuff in this condition (Fig. 6.8B, C) must be differentiated from the chronic traumatic form of this abnormality (Fig. 6.9). In the knee joint, all three compartments are commonly narrowed in a uniform manner (Fig. 6.10). The loss of the articular cartilage is caused by inflammation and pannus formation. There is little evidence of bone repair or osteophyte formation, and there is invariably associated joint effusion (Fig. 6.11). In the elbow and ankle, uniform joint space narrowing is observed (Figs. 6.12, 6.13, 6.14).
addition, cephalad migration of the humeral head may be seen secondary to destructive changes in the shoulder joint and rupture of the rotator cuff (Fig. 6.8A); resorption of the distal end of the clavicle, which assumes a pencil-like appearance, may also be observed. Tear of the rotator cuff in this condition (Fig. 6.8B, C) must be differentiated from the chronic traumatic form of this abnormality (Fig. 6.9). In the knee joint, all three compartments are commonly narrowed in a uniform manner (Fig. 6.10). The loss of the articular cartilage is caused by inflammation and pannus formation. There is little evidence of bone repair or osteophyte formation, and there is invariably associated joint effusion (Fig. 6.11). In the elbow and ankle, uniform joint space narrowing is observed (Figs. 6.12, 6.13, 6.14).
 Figure 6.6 ▪ MRI of rheumatoid arthritis of the hip joint. Coronal proton density-weighted fat-suppressed MRI (A) and coronal proton density-weighted fat-suppressed MR image (B) of the right hip joint of a 31-year-old woman obtained after intravenous administration of gadolinium show uniform narrowing of the joint space, joint effusion, synovitis, and erosions of the femoral head and acetabulum. |
 Figure 6.7 ▪ Rheumatoid arthritis of the shoulder joint. Radiograph of the left shoulder of a 70-year-old woman shows periarticular osteoporosis and concentric narrowing of the glenohumeral joint. |
Articular Erosions
Erosive destruction of a joint may be central or peripheral in location. As a rule, reparative processes are absent or very minimal; thus, there is no evidence of subchondral sclerosis or osteophytosis (Fig. 6.15), which may be present only if secondary degenerative changes are superimposed on the underlying inflammatory process (see Fig. 5.11).
Osseous Erosions
Loss of the normal radiolucent triangle between the postero-superior margin of the calcaneus and the adjacent Achilles tendon is consistent with the presence of inflammatory fluid within the retrocalcaneal bursa (Fig. 6.16A), commonly associated with erosion of the calcaneus (Fig. 6.16B-D). In the hands, the carpal bones are commonly affected (Figs. 6.17, 6.18, 6.19).
 Figure 6.8 ▪ Rheumatoid arthritis, chronic rotator cuff tear. A: Anteroposterior radiograph of the right shoulder of a 72-year-old man with advanced rheumatoid arthritis shows upward migration of the humeral head secondary to rotator cuff tear, a common complication of rheumatoid changes in the shoulder joint. Note the characteristic tapered erosion of the distal end of the clavicle, erosions of the humeral head, and the substantial degree of periarticular osteoporosis. Coronal oblique (B) and sagittal (C) proton density-weighted fat-suppressed MR images of the left shoulder of a 64-year-old woman show large articular and periarticular erosions, joint space narrowing, joint effusion, and a tear of the supraspinatus tendon (arrows), all the features of advanced rheumatoid arthritis. |
Synovial Cysts and Pseudocysts
These radiolucent defects are usually seen in close proximity to the joint (Fig. 6.20). They may or may not communicate with the joint space.
Baker Cyst
Popliteal cyst is a common finding, seen in ˜48% of patients with rheumatoid arthritis, and can be detected with ultrasound (Fig. 6.21, see also Fig. 2.76A) or with MRI (Fig. 6.22, see also Fig. 2.99). It extends posteriorly and may be directed inferiorly or superiorly in the soft tissues in the posterior aspect of the knee joint. Rupture of the Baker cyst leads to extravasation of the inflammatory content into the soft tissues of calf, producing pain and swelling that may be mistaken for thrombophlebitis (see Fig. 2.77).
Joint Effusion
Fluid can be best demonstrated in the knee joint on the lateral projection (see Fig. 6.10B). Fluid in the other large joints such as the shoulder, elbow, and hip can be best demonstrated by MRI (see Figs. 6.13 and 6.16).
Rice Bodies
Bearing macroscopic similarity to grains of polished white rice, these small, usually uniform in size intra-articular
or intrabursal loose bodies are commonly associated with rheumatoid arthritis and are thought to represent a complication of chronic inflammatory process. Occasionally, they also may be seen in seronegative inflammatory arthritis and even in tuberculous arthritis. These particles contain collagen, fibrinogen, fibrin, reticulin, elastin, mononuclear cells, blood cells, and some amorphous material (Fig. 6.23). On radiography (Fig. 6.24), this condition occasionally can be mistaken for synovial chondromatosis (see Chapter 10). On MR T1-weighted images, rice bodies exhibit intermediate signal intensity, whereas on T2 weighting, they are only slightly hyperintense relative to muscle (Figs. 6.25 and 6.26).
or intrabursal loose bodies are commonly associated with rheumatoid arthritis and are thought to represent a complication of chronic inflammatory process. Occasionally, they also may be seen in seronegative inflammatory arthritis and even in tuberculous arthritis. These particles contain collagen, fibrinogen, fibrin, reticulin, elastin, mononuclear cells, blood cells, and some amorphous material (Fig. 6.23). On radiography (Fig. 6.24), this condition occasionally can be mistaken for synovial chondromatosis (see Chapter 10). On MR T1-weighted images, rice bodies exhibit intermediate signal intensity, whereas on T2 weighting, they are only slightly hyperintense relative to muscle (Figs. 6.25 and 6.26).
 Figure 6.9 ▪ Massive posttraumatic rotator cuff tear. A: Coronal oblique proton density-weighted fat-suppressed MR arthrographic image of the right shoulder of a 32-year-old man, who sustained multiple injuries in a motorcycle accident, shows a full-thickness tear of the supraspinatus tendon (arrow). The supraspinatus muscle is medially retracted (open arrow). B: More posterior section shows also a tear of the infraspinatus tendon (arrow). Note lack of inflammatory features seen in rheumatoid arthritis. |
 Figure 6.10 ▪ Rheumatoid arthritis of the knee joints. Anteroposterior (A) and lateral (B) radiographs of the right knee of a 52-year-old woman joints show tricompartmental involvement. Note the periarticular osteoporosis, joint effusion, and lack of osteophytosis. Anteroposterior (C) and lateral (D) radiographs of both knees of a 50-year-old man show uniform narrowing of the medial, lateral, and femoropatellar joint compartments associated with joint effusions. |
 Figure 6.11 ▪ MRI of rheumatoid arthritis of the knee. Coronal T1-weighted (A) and coronal proton density-weighted (B) fat-suppressed MR images of the left knee of a 50-year-old woman show uniform joint space narrowing of the lateral and medial compartments, destruction of the articular cartilage, subchondral bone erosions, and tear of the lateral and medial menisci. C: Coronal T1-weighted MRI of the right knee of another patient demonstrates a joint effusion with inflammatory pannus (arrow). Note the lower signal intensity of the fluid as compared to the slightly higher signal of the pannus. |
 Figure 6.12 ▪ Rheumatoid arthritis of the elbow joint. Anteroposterior (A), lateral (B), and radial head-capitellum (C) views of the elbow of a 61-year-old woman show narrowing of the joint spaces, erosions of the subchondral bone of the capitellum, radial head, and trochlea, and joint effusion, manifested by the positive anterior and posterior fat-pad sign (arrows). |
 Figure 6.13 ▪ MRI of rheumatoid arthritis of the elbow joint. Coronal T1-weighted (A), coronal inversion recovery (IR) (B), and coronal (C) and sagittal (D) T1-weighted fat-suppressed MR images of the elbow joint of a 52-year-old woman, obtained after intravenous injection of gadolinium, show extensive synovitis, joint effusion, and articular erosions. |
 Figure 6.14 ▪ Rheumatoid arthritis of the ankle joints. Anteroposterior (A) and lateral (B) radiographs of the ankle show uniform joint space narrowing of the tibiotalar, subtalar, Chopart, and Lisfranc joints. |
 Figure 6.15 ▪ Rheumatoid arthritis of the hip joint. Anteroposterior radiograph of the left hip of a 59-year-old woman with advanced rheumatoid polyarthritis demonstrates the typical erosions of the femoral head and acetabulum, and acetabular protrusio. Note the lack of osteophytosis and the only very minimal reactive sclerosis. |
Rheumatoid Nodules
They are relatively common, with a reported frequency of ˜25%. They usually develop over pressure areas such as elbow (Fig. 6.27) or ischial tuberosities.
Small Joint Involvement
Rheumatoid arthritis characteristically affects the small joints of the wrist, as well as the metacarpophalangeal and proximal interphalangeal joints of the hands and feet. As a rule, the distal interphalangeal joints in the hand are spared, although in advanced stages of the disease even these may be
affected. This latter point, however, is controversial, because some investigators believe that if the distal interphalangeal joints are involved, the condition may represent juvenile idiopathic arthritis or another form of polyarthritis, not classic rheumatoid arthritis.
affected. This latter point, however, is controversial, because some investigators believe that if the distal interphalangeal joints are involved, the condition may represent juvenile idiopathic arthritis or another form of polyarthritis, not classic rheumatoid arthritis.
 Figure 6.16 ▪ Rheumatoid arthritis: osseous erosions. A: Lateral radiograph of the heel of a 49-year-old woman shows retrocalcaneal bursitis (arrow) without osseous erosions. B: Lateral radiograph of the foot of a 55-year-old woman who presented with a heel pain shows fluid in the retrocalcaneal bursa (arrow) associated with erosion of the calcaneus (curved arrow). C: Sagittal STIR MR image in another patient demonstrates bone erosion in the posterior process of the calcaneus (arrowhead) associated with extensive surrounding bone marrow edema and retrocalcaneal and retro-Achilles bursitis (arrows). D: Sagittal T1-weighted fat-saturated postcontrast MRI of the ankle in another patient demonstrates a large tibiotalar joint effusion with enhancing synovium/pannus. Note the bone erosions in the talus and navicular bones containing enhancing inflammatory pannus (arrows). |
 Figure 6.17 ▪ Rheumatoid arthritis: osseous erosions. Norgaard view of both hands of a 33-year-old woman shows early erosions of both pisiform bones (arrows). |
 Figure 6.18 ▪ Rheumatoid arthritis: osseous erosions. A: Dorsovolar radiograph of both hands of a 50-year-old woman shows erosion of the right triquetral bone (arrow). This was an isolated osseous abnormality in this patient. Coronal proton density-weighted (B) and coronal proton density-weighted (C) fat-suppressed MR images demonstrate erosion of the triquetrum associated with soft tissue edema (arrows). Note also edema in adjacent extensor carpi ulnaris tendon (arrowheads). D: Transverse US image of the same area also effectively depicts the triquetral erosion (arrow). |
 Figure 6.19 ▪ PET/CT of osseous erosion. Axial and coronal reformatted fused 18F-FDG PET/CT images of the right wrist of a 59-year-old woman with rheumatoid arthritis show high glucose uptake in the pisiform-triquetral compartment and erosion of the triquetral bone (arrows). |
 Figure 6.20 ▪ Rheumatoid cyst. Anteroposterior radiograph of the left knee of a 35-year-old woman with rheumatoid arthritis shows a large synovial cyst in the proximal tibia. Note also articular erosions and periarticular osteoporosis. |
 Figure 6.21 ▪ US of the Baker cyst. Transverse US image of the knee of a 42-year-old woman with rheumatoid arthritis shows an oval in shape hypoechoic area (arrows) that communicates with the knee joint (arrowheads). |
 Figure 6.22 ▪ MRI of the Baker cyst. Sagittal (A) and axial (B) T2-weighted fat-suppressed MR images of a 60-year-old woman with rheumatoid arthritis demonstrate a large popliteal cyst (arrows). Open arrows point to erosive changes of the articular cartilage; curved arrows indicate joint effusion. |
 Figure 6.23 ▪ Rice bodies. Photograph of fibrinous loose bodies recovered from the knee joint of the patient with rheumatoid arthritis. (From Bullough PG. Atlas of Orthopedic Pathology with Clinical and Radiologic Correlation. 2nd ed. New York, NY: Gower Medical Publishing; 1992, Fig. 11.18, p. 11.6.) |
 Figure 6.24 ▪ Rice bodies. Anteroposterior radiograph of the right shoulder of a 60-year-old woman with advanced rheumatoid arthritis demonstrates multiple rice bodies within subacromial-subdeltoid bursae complex. |
 Figure 6.25 ▪ MRI of rice bodies. Oblique coronal proton density-weighted (A), sagittal proton density-weighted (B), and oblique coronal T2-weighted (C) fat-suppressed MR images of the left shoulder of a 66-year-old woman with rheumatoid arthritis show numerous rice bodies within the shoulder joint. |
 Figure 6.26 ▪ MRI of rice bodies. Sagittal (A) and axial (B) fast spin-echo (FSE) proton density-weighted fat-suppressed MR images of the right knee of a 68-year-old woman with rheumatoid arthritis show numerous rice bodies within the joint fluid (arrows). |
 Figure 6.27 ▪ Rheumatoid nodules. A: Lateral radiograph of the right elbow of a 39-year-old man demonstrates erosions of the olecranon process (arrow), olecranon bursitis (open arrow), and rheumatoid nodules on the dorsal aspect of the forearm (curved arrows). Note the characteristic pitlike cortical erosions at the site of the rheumatoid nodules (arrowheads). B: A 68-year-old woman with rheumatoid arthritis had a large rheumatoid nodule at the lateral side of the elbow joint. Note erosions at the radiocapitellar joint (arrow). |
In addition to the characteristic changes exhibited in large joint involvement, the small joints may also show radiographic features specific for these sites.
Soft Tissue Swelling
This earliest sign of rheumatoid arthritis usually has a fusiform, symmetric shape. It is periarticular in location and represents a combination of joint effusion, edema, and tenosynovitis. Although it can be seen on the radiographs (see Fig. 6.34), the MRI provides a more effective way of demonstration of this critical feature of pre-erosive rheumatoid arthritis (Fig. 6.28). MRI also is a modality of choice to show early changes of tenosynovitis (Fig. 6.29), although ultrasound may effectively demonstrate soft tissue abnormalities at the joints (Fig. 6.30) as well as tenosynovitis in the hands and feet (Fig. 6.31, see also Figs. 2.80 and 2.81).
 Figure 6.28 ▪ MRI of very early changes of rheumatoid arthritis. Coronal STIR MR image of the hand demonstrates bone marrow edema involving the proximal phalanx and distal metacarpal of the second digit, with prominent periarticular soft tissue edema. Bone marrow edema may be seen on MRI before the bone erosions are seen on radiographs (pre-erosive edema). This feature makes MRI a good tool for establishing an early diagnosis thus leading to early therapy of rheumatoid arthritis. |
 Figure 6.29 ▪ MRI of tenosynovitis. Two axial STIR (A, B) and axial T1-weighted fat-suppressed (C) MR postcontrast images of the wrist of a 67-year-old woman with rheumatoid arthritis show synovial thickening and diffuse tenosynovitis of all flexor and extensor tendons. |
 Figure 6.30 ▪ US of small joint synovitis. A: Longitudinal ultrasound image of the left second metacarpophalangeal joint of a 60-year-old man with rheumatoid arthritis shows hypoechoic triangular area at the site of distended joint capsule, representing joint effusion and synovial thickening. B: Power Doppler color scale of the same area shows increased vascularity consistent with synovial hyperemia from active inflammation. (Reprinted with permission from Klein MJ, Bonar SF, Freemont T, et al., eds. Atlas of Nontumor Pathology. Non-neoplastic Diseases of Bones and Joints. Washington DC: American Registry of Pathology and Armed Forces Institute of Pathology, 2011, Fig. 2-17, p. 68.) |
 Figure 6.31 ▪ US and MRI of tenosynovitis. Longitudinal (A) and transverse (B) US images of the anterior aspect of the left ankle of a 65-year-old woman with rheumatoid arthritis show markedly thickened anterior tibialis tendon and fluid within the tendon sheath (arrows). C: Sagittal T1-weighted MR image confirms the thickening of the anterior tibialis tendon. D: Axial proton density-weighted fat-suppressed MR image shows in addition fluid within the anterior tibialis tendon sheath (arrows) and tenosynovitis of the peroneus longus and brevis tendons. |
Loss of Articular Cortex
This is another early radiographic sign of inflammatory arthritis: the so-called articular (or subchondral) cortex becomes indistinct or completely lost (Fig. 6.32).
Marginal Erosions
Other early radiographic signs of articular abnormalities manifest as marginal erosions at so-called bare areas. These are the sites within the joint capsule that are not covered by articular cartilage (Fig. 6.33). The most common locations for these erosions are the radial aspects of the second and third metacarpal heads and the radial and ulnar aspects of the bases of the proximal phalanges (Fig. 6.34). Synovial inflammation in the prestyloid recess, a diverticulum of the radiocarpal joint that is intimate with the styloid process of ulna, as Resnick pointed out, produces marginal erosion of the styloid tip.
 Figure 6.32 ▪ Rheumatoid arthritis—loss of articular cortex. A: Very early radiographic feature is the loss of so-called articular cortex of the metacarpal head on the radial aspect (arrow). Compare with the intact outline of the normal third and fourth metacarpal heads. B: In another patient, the metatarsal heads are affected in similar manner (arrows), but to a slightly greater extent. |
 Figure 6.33 ▪ Rheumatoid arthritis—erosions in bare areas. Invasion of inflammatory pannus (P) into the articular areas not covered by the articular cartilage (so-called bare areas) causes marginal erosions (arrows). |
Articular Erosions
In more advanced stages of rheumatoid arthritis, articular erosions are commonly seen. In the hand, the metacarpophalangeal and proximal interphalangeal joints are usually affected (Fig. 6.35) as well as joints of the wrist (Figs. 6.36 and 6.37, see also Fig. 6.35A). In the foot, the metatarsophalangeal and proximal interphalangeal joints are commonly affected (Figs. 6.38 and 6.39). The subtalar joint may be affected as well (Fig. 6.40).
Joint Deformities
Although not pathognomonic for rheumatoid arthritis, certain deformations such as the swan-neck deformity and the boutonniére deformity are more often seen in this form of arthritis than in other inflammatory arthritides. The first of these represents hyperextension in the proximal interphalangeal joint and flexion in the distal interphalangeal joint, a configuration resembling a swan’s neck (Fig. 6.41, see also Fig. 1.3C). In the boutonniére deformity, the configuration is just the opposite, with flexion in the proximal joint and extension in the distal interphalangeal joint (Fig. 6.42, see also Fig. 1.3A, B). The word boutonniére is French for “buttonhole,” the term for this deformity deriving from the configuration of the finger while securing a flower to a lapel. A similar deformation of the thumb is called hitchhiker’s thumb (see Fig. 1.2).
Moreover, subluxations and dislocations with malalignment of the fingers are common findings in advanced stages of rheumatoid arthritis. Particularly characteristic are ulnar deviation of the fingers in the metacarpophalangeal joints and
radial deviation of the wrist in the radiocarpal articulation (Fig. 6.43). In far-advanced stages of rheumatoid arthritis, shortening of several phalanges may be encountered secondary to destructive changes in the joints associated with dislocations in the metacarpophalangeal joints. This deformity appears as a “telescoping” of the fingers, hence its name, main en lorgnette, from the French name for the telescoping type of opera glass (Fig. 6.44). An abnormally wide space between the lunate and the scaphoid may also be encountered in advanced stages of the disease secondary to erosion and rupture of the scapholunate ligament (Fig. 6.45); this phenomenon is known in the literature as the Terry-Thomas sign. Joint deformities are also often seen in the foot, and subluxation in the metatarsophalangeal joints often leads to deformities such as hallux valgus and hammer toes (Fig. 6.46).
radial deviation of the wrist in the radiocarpal articulation (Fig. 6.43). In far-advanced stages of rheumatoid arthritis, shortening of several phalanges may be encountered secondary to destructive changes in the joints associated with dislocations in the metacarpophalangeal joints. This deformity appears as a “telescoping” of the fingers, hence its name, main en lorgnette, from the French name for the telescoping type of opera glass (Fig. 6.44). An abnormally wide space between the lunate and the scaphoid may also be encountered in advanced stages of the disease secondary to erosion and rupture of the scapholunate ligament (Fig. 6.45); this phenomenon is known in the literature as the Terry-Thomas sign. Joint deformities are also often seen in the foot, and subluxation in the metatarsophalangeal joints often leads to deformities such as hallux valgus and hammer toes (Fig. 6.46).
 Figure 6.34 ▪ Rheumatoid arthritis—erosions in bare areas. A: Typical erosions in the bare areas are seen in this 55-year-old woman with rheumatoid arthritis. Note also periarticular osteoporosis and soft tissue swelling. B: Radiograph of the index finger shows erosion in the bare area at the base of the proximal phalanx (arrow) associated with soft tissue swelling. C: Radiograph of the middle finger of another patient shows erosions in the bare areas at the distal end of the proximal phalanx (arrows). |
 Figure 6.35 ▪ Rheumatoid arthritis of the hands. A: Dorsovolar radiograph of both hands of a 63-year-old woman shows typical for this disease loss of articular cartilage and subchondral erosions affecting predominantly metacarpophalangeal, radiocarpal, and intercarpal joints. Observe that the distal interphalangeal joints are spared. B: Dorsovolar radiograph of both hands of a 72-year-old woman shows articular erosions affecting metacarpophalangeal joints of both hands. The proximal interphalangeal joints of the left hand are also affected. The distal interphalangeal joints are normal. |
 Figure 6.36 ▪ CT of rheumatoid arthritis of the wrist. Coronal (A) and sagittal (B) reformatted CT images of the left wrist of a 39-year-old woman show erosions of the radiocarpal joint and erosions of the several carpal bones. |
 Figure 6.37 ▪ MRI of rheumatoid arthritis of the wrist. Coronal (A) and axial (B) T1-weighted fat-suppressed MR images of the right wrist of a 60-year-old woman, obtained after intravenous administration of gadolinium, show erosions of the ulnar styloid and several carpal bones including the scaphoid, lunate, triquetrum, capitate, and hamate. There are also erosions of the second and third carpometacarpal joints. Note in addition extensive synovitis exhibiting high signal intensity. |
 Figure 6.38 ▪ Rheumatoid arthritis of the feet. Dorsoplantar radiograph of both feet of a 55-year-old woman shows erosions and subluxations of metatarsophalangeal joints. |
 Figure 6.39 ▪ MRI of rheumatoid arthritis of the foot. Long-axis T1-weighted (A), long-axis proton density-weighted fat-suppressed (B), and short-axis T1-weighted fat-suppressed (C) postcontrast MR images of the left foot of a 64-year-old woman show erosions of the second, third, and fourth metatarsophalangeal joints (arrows) accompanied by synovitis. |
Joint Ankyloses
A rare finding that may be observed in advanced stages of rheumatoid arthritis is joint ankylosis, which is most commonly encountered in the midcarpal articulations (see Figs. 6.43 and 6.44). Ankylotic changes in the wrist are more common in patients with juvenile idiopathic arthritis and with so-called seronegative rheumatoid arthritis.
 Figure 6.40 ▪ CT of rheumatoid arthritis of the foot. A and B: Two sagittal reformatted CT images of the hindfoot of a 52-year-old man show erosions of the subtalar and calcaneocuboid joints.
Related posts: Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
Get Clinical Tree app for offline access
|
