A Systematic Approach to Differentiating Joint Disorders A

MedicalContinuing Education

PODIATRIC RADIOGRAPHY

Objectives After completing this mate- rial the reader shall be able to: 1) List the radiographic criteria for systematically evaluating joints and joint disease. 2) Define: joint effusion, AA SystematicSystematic arthritis mutilans, and enthesopathy. 3) List common joint dis- ApproachApproach toto orders that are associated with arthritis. 4) Explain the importance DifferentiatingDifferentiating of a lesion (erosion, for example) having either a well- defined or ill-defined margin. JointJoint DisordersDisorders 5) List target areas in the foot and calcaneus for com- X-rays can be an important mon arthritic disorders. 6) Distinguish between tool in confirming your the joint disorders (based diagnosis. on radiographic findings).

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By Robert A. Christman, D.P.M. out question, osteoarthritis is the not unusual for the inflammatory most common, primarily because rheumatic diseases (rheumatoid everal arthritides (types of of the mechanical wear and tear arthritis, psoriatic arthritis, anky- arthritis) have a predilection that weight-bearing activities losing spondylitis, and Reiter’s Sfor the foot (Table 1). With- place on cartilage. However, it is Continued on page 186 www.podiatrym.com APRIL/MAY 2004 • PODIATRY MANAGEMENT 185 Joint Disorders... The archetypal radiographic consider the probable differential presentations of joint disorders diagnoses. Continuingsyndrome) to first appear or that have been described in the be diagnosed in the feet. Fur- literature are not necessarily what Systematic Approach to Medical Education thermore, gouty arthritis and dia- the clinician encounters in every- Differentiating Joint Disorders betic neuropathic osteoarthropa- day practice. The classic picture is A detailed, systematic ap- thy target have a predilection for typically the patient who was di- proach for evaluating pedal joints the foot. agnosed with the joint disease entails three considerations2 many years or even decades ago. In contrast, the patient with acute symptomatology may ini- TABLE 1 tially come for help at the onset of disease or soon thereafter. In To maximize the Joint Disorders such a case, the radiographic detection of early findings are frequently subtle and Affecting nonspecific, the clinical findings arthritis, you “must the Foot are vague, and the diagnosis is know how to look, often elusive. Furthermore, atypi- where to look, and what Osteoarthritis cal cases are common. The chal- lenge, therefore, is to identify the Rheumatoid arthritis to look for.” subtle, early radiographic find- Psoriatic arthritis ings, because the classic features Reiter’s syndrome of a particular joint disorder do Ankylosing spondylitis not manifest until many years later. To maximize the detection (Table 2). For obvious reasons, the Gouty arthritis of early arthritis, you “must know symptomatic joint or joints are as- Neuropathic osteoarthropathy how to look, where to look, and sessed first. The asymptomatic Septic arthritis what to look for.”1 Then, along joints of both extremities should with the clinical and other labo- also be evaluated, for two reasons: ratory findings, you must list and Most joint disorders target both extremities, and joints may be affected that are clinically asymptomatic. (Joint disease is one of TABLE 2 the few conditions that warrants performing a bilateral radiograph- A Systematic Approach to Evaluating ic study.) The examination does- n’t stop here, however. Sites dis- Joint Disease tant from involved joints, osseous and soft tissue are also considered. Roentgen features at or adjacent to involved joints Abnormal findings at the cal- Primary findings caneal entheses and heel pain, for Osseous erosion example, can be associated with New bone formation joint disease. Finally, the distribu- Joint space alteration tion of radiographic findings must 3 Secondary findings be assessed for specific patterns. Many articular disorders demon- Soft tissue edema strate characteristic patterns of Calcification joint involvement that help dis- Geographic rarefaction tinguish one disease from another. Alignment abnormalities Articular disorders affecting Roentgen features at sites distant from involved joints the foot may involve one or mul- Erosion tiple joints. Monoarticular joint Enthesopathy disease is generally attributed to either trauma, infection, or acute Soft tissue mass gouty arthritis (Table 3). Less com- Patterns of joint disease according to distribution of roentgen findings mon causes of pedal monoarticu- Joints involved lar disease include rheumatoid Targeted joints monoarthritis and pigmented vil- Bilateral versus unilateral lonodular synovitis. Examples of Symmetry versus asymmetry polyarticular joint disorders affect- Extra-articular sites involved ing the foot include osteoarthritis, rheumatoid arthritis, seronegative Continued on page 187

186 PODIATRY MANAGEMENT • APRIL/MAY 2004 www.podiatrym.com MedicalContinuing Education the atrophic joint disorders. A subdivision of this TABLE 3 group is commonly associated with an adjacent soft tissue mass Causes of Joint Disease clinically and the preservation of joint space. Forrester and Brown have used the term “lumpy-bumpy” joint Monoarticular disease to characterize this latter Trauma group..4 Infection Neuropathic osteoarthropathy is Crystal deposition divided into two subtypes: forefoot, Gout and the combined midfoot and tar- CPPD sus. Its radiographic features vary de- Rheumatoid monoarthritis pending on location: Forefoot sites exhibit findings characteristic of at- Pigmented villonodular synovitis rophic joint disease; the midfoot and Polyarticular tarsal sites display features of detritus Osteoarthritis (hypertrophic) arthritis. Rheumatoid arthritis Each of the roentgen features Seronegative arthritis associated with joint disease is discussed individually in the following Chronic tophaceous gout sections. Remember the radio- Neuropathic osteoarthropathy graphic categories of joint disor- Pigmented villonodular synovitis (midfoot) ders; you can recognize associations Multiple reticulohistiocytosis between certain roentgen findings and arthritis categories, improving your diagnostic acumen. arthritis (psoriatic arthritis, anky- ing pathologic processes: losing spondylitis, and Reiter’s syn- degenerative, inflamma- drome), neuropathic osteoarthropa- tory, and metabolic4 thy, and chronic tophaceous gout. (Table 4). This classifica- Differentiation of joint disorders tion, unfortunately, does can be simplified by applying a gener- not include neuropathic al classification system to the present- osteoarthropathy. In ing features. One categorization of 1904, Goldthwaite used arthritis has been based on underly- radiographic criteria to distinguish between osteoarthritis and rheumatoid arthritis.5 These crite- TABLE 4 ria can be expanded to include the remaining Categories of forms of pedal arthritis. Joint disorders affect- Joint Disease ing the foot can be divid- (based on underlying ed into two radiographic categories, based on the pathology) predominant radiographic feature: hypertrophic Degenerative and atrophic (Table 5). Osteoarthritis Hypertrophic joint dis- Figure 1. Irregular, ill-defined erosion (ankylosing Inflammatory ease features bone over- spondylitis). Rheumatoid arthritis growth and enlargement. The characteristic findings are sub- Roentgen Features at Involved Seronegative arthritis chondral sclerosis and osteophyte for- Joints: Primary Findings Psoriatic arthritis mation at the margin of a joint. Detri- Reiter’s disease tus arthritis, a subcategory of hyper- Osseous Erosion Ankylosing spondylitis trophic arthritis, includes those disor- Bone erosion is a primary fea- ders that exhibit fragmentation in ad- ture of all joint disorders except Septic arthritis dition to exaggerated hypertrophic hypertrophic joint disease. Gener- Metabolic features. The loss of bone substance, ally speaking, erosion associated Gouty arthritis primarily through erosion, and joint with active atrophic joint disease space narrowing, with or without pe- appears small, ill defined, and ir- riarticular osteoporosis, characterize Continued on page 188 www.podiatrym.com APRIL/MAY 2004 • PODIATRY MANAGEMENT 187 Joint Disorders... Continuingregular (Figure 1). This char- TABLE 5 acterization contrasts with the Medical Education larger, well-defined C-shaped erosion classically seen in the disor- Categories of Joint Disease ders associated with an adjacent (based on radiographic features) soft tissue mass (Figure 2). Erosion associated with gouty arthritis, Hypertrophic joint disease however, is indistinguishable early Osteoarthritis in the disease process, but preser- Detritus arthritis vation of joint space and target involvement of the first metatar- Post-traumatic arthritis sophalangeal joint differentiate Tarsus and midfoot neuropathic osteoarthropathy gouty arthritis from the other in- Atrophic joint disease Rheumatoid arthritis Seronegative arthritis Psoriatic arthritis Ankylosing spondylitis Reiter’s disease Septic arthritis Forefoot neuropathic osteoarthropathy

Associated with adjacent soft tissue mass and preservation of joint space

Gouty arthritis Multiple reticulohistiocytosis Pigmented villonodular synovitis

flammatory rheumatic disease in the thin white line that compris- the proper clinical setting. The es the subchondral bone plate presence of an erosion excludes (Figure 4). Eventually the local- Figure 2. Well-defined, C-shaped ero- osteoarthritis as a primary diagno- Continued on page 189 sion (gouty arthritis). sis; however, both a trauma-in- duced subchondral bone defect and a subchondral bone cyst can mimic the appearance of an ero- TABLE 6 sion (Figure 3). Erosion is an early finding in Arthritis the course of an inflammatory joint disease. The erosions are Mutilans intra-articular and typically begin along the medial or lateral Figurative terms margins of the joint. Between Pencil-in-cup deformity where the cartilage ends and the Mortar and pestle joint capsule inserts is a bony surface covered only by perios- Sucked candy stick teum or perichondrium.3 This Whittling surface is in contact with the Differential diagnosis synovium and its fluid and is Psoriatic arthritis known as the “bare” area. The in- Forefoot neuropathic flamed synovium, known as pannus, invades the bone; on a ra- osteoarthropathy diograph, the outer margin of Rheumatoid arthritis subchondral bone quickly disap- (fifth metatarso- pears. Initially this disappearance phalangeal joint) Figure 3. Subchondral bone cyst mim- may be as subtle as a “dot-dash” icking an erosion. appearance or “skipping” along

188 PODIATRY MANAGEMENT • APRIL/MAY 2004 www.podiatrym.com MedicalContinuing Education Joint Disorders... sure atrophy secondary to direct apposition of a ized loss of marginal bone (de- soft tissue mass with con- creased density) progresses so far comitant infiltration and re- that the form of the affected placement of bone (Figure 2). It bone appears abnormal. These may or may not be intra-articular findings may be recognized days in location. Or it may result or weeks after the onset of symp- months or years after an acute, ill- toms and contribute to the ero- defined erosion remodels. sion’s ill-defined and irregular Erosions that involve both appearance. margins of any metatarsopha- The well-defined erosion, in langeal or interphalangeal joint contrast, appears radiographically can result in a condition known as several months or years after the arthritis mutilans. Arthritis muti- initial onset of symptoms. It fre- Figure 4. Early rheumatoid arthritis: lans, also called resorptive quently results from chronic pres- Dot-dash or skip pattern. arthropathy, is characterized by concentric bone resorption and primary joint destruction.4 Bone resorption may even expand to in- TABLE 7 clude the nearby metadiaphyseal cortex. This has figuratively been Forms of Bone Production and described by several terms, most commonly the “pencil-in-cup” de- Associated Joint Disorders

Osteophyte Osteoarthritis Subchondral sclerosis Hypertrophic joint Osteoarthritis Neuropathic osteoarthropathy (midfoot and tarsus) disease features bone Periostitis overgrowth and Seronegative arthritis enlargement. Psoriatic Reiter’s Septic arthritis Forefoot neuropathic osteoarthropathy Overhanging margin (Martel’s sign) formity. Other terms used to de- Gouty arthritis scribe arthritis mutilans are listed Whiskering in Table 6. This presentation has characteristically been associated Psoriatic arthritis Ivory phalanx with psoriatic arthritis (Figure 5). Psoriatic arthritis However, forefoot neuropathic osteoarthropathy and rheumatoid arthritis at the fifth metatarsophalangeal joint (Figures 6 and 7) present similar pictures. TABLE 8 New Bone Formation The predominant feature of Grouping of Joint Disease Based on hypertrophic joint disease is bone Joint Space Alteration production. Osteophytosis and subchondral sclerosis are charac- JOINT SPACE ARTHRITIS teristic radiographic findings. Bone production, however, can Nonuniform narrowing Degenerative arthritis show other forms, including pe- Uniform narrowing Inflammatory arthritis riostitis, whiskering, and cortical Normal or near normal joint space Miscellaneous arthritis and trabecular thickening. This latter group of examples is not From Kaye JJ: Radiology 177(3):601, 1990. seen with hypertrophic joint disease but is frequently associated Continued on page 190 www.podiatrym.com APRIL/MAY 2004 • PODIATRY MANAGEMENT 189 Joint Disorders... chondral sclerosis represents bone pro- Continuingwith seronegative arthritis. duction and is not a TABLE 9 New bone production is rarely primary feature of Medical Education seen at joints affected by rheuma- the atrophic and Differential Diagnosis toid arthritis. An overhanging soft tissue erosive margin of new bone is frequently joint disorders. of Enthesopathy associated with the C-shaped ero- The presence of sions encountered with gouty periostitis near the in the Foot arthritis. Table 7 lists the varying metaphysis of a forms of bone production and as- symptomatic Trauma sociated joint disorders. metatarsophalangeal Degenerative disease An osteophyte is a spur at the or interphalangeal Osteoarthritis margin of a joint (Figure 8). It is a joint is highly sug- Diffuse idiopathic skeletal hyperostosis gestive of seronega- Inflammatory joint disease tive arthritis (Figure 9). Unfortunately Rheumatoid arthritis the periostitis is Seronegative arthritis Arthritis mutilans, also short-lived: Within Crystal deposition disease called resorptive a few weeks it quick- CPPD (probable) ly remodels and be- HADD (probable) arthropathy, is come continuous characterized by with the bony margin. Periostitis may Gout (possible) concentric bone also be seen with Endocrine disorders resorption and primary septic arthritis and Diabetes mellitus joint destruction. forefoot neuropathic osteoarthropathy. The latter disease is difficult to differentiate from in- is characteristically seen at the fection. hallux and, less frequently, the classic feature of osteoarthritis. A variation of periostitis seen lesser-digit distal interphalangeal Numerous figurative terms have particularly with psoriatic arthritis joints (Figure 10). Ill-defined scle- been applied to this lesion, in- is referred to as “whiskering,” be- rosis accompanies this finding. cluding dorsal flag (along the first- cause it resembles the stubble of Whiskering appears to represent metatarsal head), lipping (if at new beard concomitant both sides of the joint), and growth.6 Its new bone beaking. spiculated ap- formation Subchondral sclerosis is also pearance radi- and erosion referred to as eburnation (Figure ates away at the capsu- 8). It is, rarely, seen in the absence from the bone lar and liga- of joint space narrowing. Sub- margin, and it mentous entheses. Occasion- ally the distal phalanx of an affected digit becomes quite dense or sclerotic relative to normal bone density. This is seen especially in the hallux (Fig- ure 11). Known as the “ivory” phalanx, it is another presen- Figure 6. Arthritis mutilans: Neuropathic os- tation associ- Figure 5. Arthritis mutilans: Psoriatic arthritis. teoarthropathy. Cont’d on page 191

190 PODIATRY MANAGEMENT • APRIL/MAY 2004 www.podiatrym.com MedicalContinuing Education Joint Disorders... ated, in the proper clinical setting, Erosion or lysis of the with psoriatic arthritis.7 articular cartilage eventu- The well-defined erosions of ally appears as joint space gouty arthritis occasionally have narrowing, as the two opposing an overhanging margin of new surfaces retract on one another. bone (Figure 12). This finding, de- This is an early radiographic find- scribed by Martel8 represents new ing with inflammatory joint disor- bone production at the margin of ders such as rheumatoid or septic an erosion. The body seems to be arthritis. Joint space narrowing responding to the presence of the may be either even or uneven. tophus and attempting to encap- The narrowing seen with inflam- sulate it or wall it matory arthritis off. The over- usually is even hanging margin or uniform of bone is not an across the joint uncommon find- (Figure 14). This ing. Its presence Excess fluid is because in- strongly suggests accumulates in a joint flammatory pan- gouty arthritis. nus is found Another finding that is acutely throughout the sometimes associ- inflamed. joint and affects ated with the ero- all cartilage. In sions of gouty contrast, os- arthritis is sur- teoarthritis sec- rounding sclero- ondary to wear sis. and tear or trauma usually only involves a seg- Joint Space Alteration ment of the cartilage or subchon- Normal, widened, or narrowed dral bone, not the entire surface. joint spaces may be seen with ar- As a result, narrowing of the joint ticular disorders. Kaye has corre- space has an uneven or nonuni- lated the types of joint space alter- form presentation radiographical- ation with three groups of arthri- ly (Figure 15). The unaffected tides9 (Table 8). This table, along joint segment has normal spacing. with the remaining radiographic The presence of a normal joint Figure 7. Arthritis mutilans: Rheuma- and clinical information, offers Continued on page 192 toid arthritis (fifth-metatarsopha- valuable information that can lead langeal joint). to diagnosis of the arthritis in question. Excess fluid accumulates in a joint that is acutely inflamed. To accommodate this fluid, the capsule becomes stretched and the opposing bones are distracted. Ra- diographically this may appear as widening of the joint space. Un- fortunately, joint space widening secondary to acute synovitis is a very subtle finding. Furthermore, the finding is short-lived; its radiographic presence is a hit-or- miss incident. Extensive erosion of subchondral bone also gives the appearance of joint space widening (Figure 13). Erosion and subse- quent fibrous tissue deposition between bones contribute to the widening seen in psoriatic arthri- 2 Figure 8. Osteoarthritis, first tis. metatarsophalangeal joint. Osteo- The joint space seen radio- phytes (white arrows) and subchon- graphically corresponds to the car- Figure 9. Psoriatic arthritis: Periosti- dral sclerosis (black arrows). tilage lining each bony surface. tis. www.podiatrym.com APRIL/MAY 2004 • PODIATRY MANAGEMENT 191 Joint Disorders... rectly involved until much later in the course of disease. As a result, Continuingspace associated with periar- the presence of normal joint space ticular erosion is characteristic in light of obvious erosion is a Medical Education of joint disorders associated with characteristic finding. This is in soft tissue masses strict contrast to (Figure 16). inflammatory Chronic topha- joint disease. The ceous gout, for aggressive nature example, is not of this latter primarily an in- Increased soft tissue group of disor- flammatory dis- ders and associ- order. Although density and volume ated intense syn- intense inflam- secondary to ovitis quite mation is clini- rapidly cause cally seen with synovitis is known as bone and carti- acute attacks of joint effusion. lage destruction. gout, these symp- Bony or fi- toms last only a brous ankylosis short period of may occur be- Figure 12 Gouty arthritis: Martel’s time. Several tween two joint sign. years may lapse surfaces as an end before radiographic evidence of stage of some joint diseases. This is other site. It is viewed radiograph- joint disease is evident. Further- especially true of the inflammatory ically as an increased soft tissue more, many of the erosions associ- joint disorders. Bony ankylosis is density and/or volume relative to ated with gouty arthritis are peri- more commonly associated with normal expectation. Generalized articular, outside the capsule. seronegative arthritis and septic soft tissue edema can be related to Therefore cartilage may not be di- arthritis. The interphalangeal joints abnormal systemic conditions (cardiac disease, acromegaly), diffuse inflammatory states (celluli- tis), or peripheral vascular disease (venous insufficiency, lymphede- ma).4 It is not, however, a primary finding in joint disorders. Many patients with pedal joint disease have concomitant generalized soft tissue edema that is secondary to the conditions just noted. Regional soft tissue edema is confined to a smaller segment of the body. An entire digit, for example, may be edematous from acute inflammatory conditions including infection, seronegative Figure 10. Psoriatic arthritis: Whiskering at hallux. arthritis (the so-called sausage toe), and gout. The edema associ- are targeted in psoriatic arthritis. ated with an acute gouty attack at Midfoot ankylosis may be seen in the first metatarsophalangeal the rheumatoid foot (Figure 17). joint may extend to the midfoot. Ankylosis is seldom seen with This clinical presentation may gouty arthritis and is not associated certainly mimic an infectious with pedal osteoarthritis. However, process. Post-traumatic states also the superimposition of osteophytes can show regional soft tissue and joint space narrowing may edema. Neuropathic os- simulate bony ankylosis. teoarthropathy of the midfoot and tarsus shows either regional Roentgen Features at Involved or diffuse edema. Joints: Secondary Findings Localized soft tissue edema may be related to synovial inflam- Soft Tissue Edema and Masses mation or to a mass. The edema Soft tissue edema may be gen- associated with synovitis sur- Figure 11. Psoriatic arthritis: Ivory eralized throughout the foot, re- rounds the joint and is quite well phalanx. gional, or localized to a joint or Continued on page 193

192 PODIATRY MANAGEMENT • APRIL/MAY 2004 www.podiatrym.com MedicalContinuing Education Joint Disorders... Periarticular soft tissue masses However, masses associ- are associated with a few joint dis- ated with multiple reticu- defined radiographically. In- orders. The most common exam- lohistiocytosis are wide- creased soft tissue density and vol- ple is the gouty tophus. Tophi are spread, symmetric, and noncal- ume secondary to synovitis is well-defined masses that are found cifying. known as joint effusion. This con- adjacent to joints or at extra-artic- Soft tissue masses are occasion- dition, although nonspecific, is ular sites (Figure ally seen with highly associated with inflamma- 18). They occa- rheumatoid tory joint disease. However, syn- sionally exhibit arthritis. ovitis secondary to trauma, either calcification (see In the foot, Rheumatoid acute or chronic and repetitive, following discus- nodules are sel- appears radiographically identical sion). Lesions are radiographic dom found in to that caused by inflammatory distributed asym- visualization of calcified the foot but, rheumatic disease (rheumatoid metrically in the when present, and seronegative arthritis). In foot. crystals is best may radiographi- acute attacks of gout, the edema is Tophi may be appreciated in the cally appear in- pronounced. It often mimics the seen several years distinguishable diffuse edema associated with in- after the initial periarticular soft from a gouty to- fection. onset of symp- tissues. phus except that toms. the former rarely They are calcifies.11 a charac- Soft tissue tu- teristic feature of chronic mors and tumor-like lesions may tophaceous gout and may manifest in periarticular locations or may not be associated and cause articular erosions. Al- with erosions; the latter though not common, an example develop adjacent to tophi. of one such lesion occurring in It has been reported that the foot is pigmented villonodular the clinical presence of synovitis. As a rule, it is monoar- tophi are strongly associ- ticular. However, a rare, polyartic- ated with the characteris- ular manifestation can appear in tic radiographic features the midfoot (Figure 19). This is of gouty arthritis.10 probably related to the unique Another soft tissue ero- synovial compartmentalization in sive joint disorder is mul- this anatomic region. Well-de- tiple reticulohistiocytosis. fined erosions develop adjacent to These masses radiographi- soft tissue masses. cally appear similar to Continued on page 194 Figure 13. Psoriatic arthritis: Joint space widen- those seen ing secondary to erosion. in gout.

Figure 14. Rheumatoid arthritis: Even joint space narrow- Figure 15. Osteoarthritis: Uneven joint space narrowing. ing. www.podiatrym.com APRIL/MAY 2004 • PODIATRY MANAGEMENT 193 Joint Disorders... ic. Dystrophic calcifications occur in soft tissues that are damaged ContinuingCalcification or altered but have no underlying Numerous disorders are asso- disturbance in calcium or phos- Medical Education ciated with soft tissue calcifica- phorus metabolism.12,13 tion in the foot. Widespread soft Soft tissue calcifications, tissue calcification in otherwise when associated with joint dis- normal tissues is associated with ease, may be diagnostic for a disorders that demonstrate ele- group of disorders known as the vated calcium or phosphate levels crystal deposition diseases. They in the serum. Hyperparathy- are monosodium urate crystal roidism, for example, may cause deposition disease (gouty arthri- diffuse periarticular, capsular, tis), calcium pyrophosphate di- and vessel calcification. The ma- hydrate (CPPD) deposition dis- jority of soft tissue calcifications ease, and hydroxyapatite crystal seen in the foot, however, are deposition disease (HADD). Cal- probably dystrophic or idiopath- cifications can be found in the periarticular tissues, joint capsule, or cartilage. The crystals associated with Figure 18. Gout: Tophus at hallux in- gouty arthritis may be deposited terphalangeal joint.

TABLE 10 Target Joints

Osteoarthritis First MPJ Rheumatoid arthritis All MPJs Psoriatic arthritis Lesser MPJs, hallux IPJ, DIPJs Gout First MPJ Neuropathic osteoarthropathy Tarsometatarsal and intertarsal joints

MPJ, Metatarsophalangeal joint; IPJ, interphalangeal joint; DIPJ, distal interphalangeal joint. Figure 16. Gout: Sparing of joint space despite erosive disease. in the joint capsule, synovium, cartilage, subchondral bone, or periarticular tissues.14 A collection of monosodium urate crystals in the soft tissues is known as a tophus. In the foot, radiographic visualization of calcified crystals is best appreciated in the periarticular soft tissues. Tophus calcification is occasionally seen with tophaceous gout. Although not a pathognomonic finding, calcification of a periarticular soft tissue mass, especially if situated adja- A B cent to an erosion, is highly suggestive of gouty Figure 17. Bony ankylosis. A, Psoriatic arthritis. B, Rheumatoid arthritis. Continued on page 195

194 PODIATRY MANAGEMENT • APRIL/MAY 2004 www.podiatrym.com MedicalContinuing Education Joint Disorders... findings are known as pyrophos- and architecture. They phate arthropathy when associat- are not uncommon in os- arthritis in the proper clinical set- ed with CPPD deposition. Calcifi- teoarthritic joints (Figure ting. Small, punctate calcifications cations can occur in articular and 21). Trauma can cause osteo- can be identified in the soft tissue periarticular soft tissues. However, phytes or subchondral bone with mass (Figure 20). cartilage calcification, or chondro- overlying cartilage to break off. calcinosis, has re- These fragments of bone and/or ceived the most atten- cartilage can float or become tion. The primary crys- wedged within the joint or syn- tal associated with chondrocalcinosis appears to be CPPD. Little has been reported in the literature Monosodium urate regarding pedal CPPD crystals, typically involvement. Perhaps this is because micro- deposited in the soft scopic examination for tissues in patients with crystals is not per- formed routinely for gout, may also be the workup of acutely deposited in bone. symptomatic joints. However, the literature refers to metatarsophalangeal, tarsal, and ankle joint in- ovium. Because many of these volvement.16 Chondro- loose bodies contain cartilage, calcinosis is not readi- faint calcifications may be identi- Figure 19. Pigmented villonodular synovitis, tarsus. ly recognized at the fied. They tend to enlarge over tarsal joints, because time. Large osseous bodies or frag- Calcium pyrophosphate dihy- other bones are superimposed. ments and concomitant severe hydrate (CPPD) deposition disease is Magnification radiography associated with several patterns of using high-detail industrial joint involvement.15 In general, ra- x-ray film may be neces- diographic features include soft sary to see the subtle tissue calcification, joint space metatarsophalangeal joint narrowing, subchondral sclerosis, calcifications.17 and fragmentation. The latter Calcification of periarticular structures, including tendons and bursae, is also seen with hydroxyapatite crystal deposition disease (HADD).18 The clinical course may mimic the sin- gle-joint symptomatology seen with gout and pseudo- gout.19 The radiographic presentation of HADD, also referred to as calcifying tendonitis, consists of round or oval calcifications Figure 21. Loose bodies. within the course of a tendon.20 Linear or punctate calcific pertrophic joint disease in tarsal densities may be seen along the joints are suggestive of either margins of affected joints. Anoth- post-traumatic arthritis or neuro- er presentation can be a rather pathic osteoarthropathy (Figure large, amorphous calcification ad- 22). jacent to a joint. Calcifications and ossifications Geographic Rarefaction may be seen in the joint itself and Subchondral bone cysts occa- are referred to as loose bodies. sionally accompany arthritis. Loose osseous bodies (“joint They appear as geographic, lytic Figure 20. Gout: Calcified tophus. mice”) vary considerably in size Continued on page 196 www.podiatrym.com APRIL/MAY 2004 • PODIATRY MANAGEMENT 195 Joint Disorders... thought to be pannus invading calized in the medial and superior the subchondral bone.24 aspects of the first-metatarsal Continuinglesions and may mimic ero- Monosodium urate crystals, head (Figure 24). Although this sions viewed en face. This is typically deposit- finding is non- Medical Education especially true along the medial ed in the soft tis- specific, in the aspect of the first-metatarsal sues in patients proper clinical head. The typical subchondral with gout, may setting it sug- cyst with sclerotic margin is com- also be deposited gests gouty monly associated with degenera- in bone.25 This Subluxation and arthritis. 21 tive joint disease (see Figures 3 deposition has dislocation are & 15). Its pathogenesis is contro- been associated Alignment Ab- versial; the two probable mecha- with chronic frequently encountered normalities nisms are bone contusion22 and tophaceous gout. in the rheumatoid Positional de- synovial intrusion.23 Subchondral Multiple focal, formities may be cystic lesions have also been asso- geographic areas forefoot. encountered ciated with rheumatoid arthritis of bone loss (rar- with joint disor- (Figure 23). They have been re- efaction) are seen ders. Abnormali- ferred to as pseudocysts. Their ra- at these sites (see ties range from diographic appearance is identi- Figure 16). I have nonspecific mis- cal to the degenerative cyst but observed in a retrospective study alignment of two bones to sublux- lacks a sclerotic margin.17 The of a large group of patients that ation and dislocation. mechanism of formation is localized rarefaction at the first A finding commonly associat- metatar- ed with rheumatoid arthritis is sopha- fibular deviation of the digits, es- langeal pecially the hallux (Figure 25A). joint with This finding generally does not in- the absence volve the fifth digit, however. The of erosion constraints of shoe gear probably is frequent- prevent lateral deviation of this ly an early toe. Erosion may or may not ac- radiograph- company misalignment. Digital ic finding deviation in a fibular direction is in gouty not found in all instances of arthritis. rheumatoid arthritis. Tibial devia- The rarefaction may also be encountered (Fig- tion is lo- Continued on page 197

Figure 22. Detritus arthritis: Tarsal neuropathic osteoarthropathy.

Figure 24. Early gout: Rarefaction first-metatarsal Figure 23. Rheumatoid arthritis: Pseudocyst. head.

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noted when the talocal- caneal joint is involved. Misalign- ment between two articular surfaces can result in cartilage damage and subse- quent osteoarthritis. A B Examples include hallux Figure 25. Rheumatoid arthritis. A, Fibular deviation. B, Tibial deviation. (Courtesy Irwin Juda, D.P.M., Philadelphia) abductovalgus and ure 25B). It is important to note the lateral view, although it is other medial column misalign- that hallux abductovalgus and difficult to visualize the joint ments associated with pes planus lesser-toe deformities are nonspe- structures because the adjacent and pes cavus. cific; these abnormalities are fre- osseous structures are superim- Pes planovalgus is a frequent quently seen in the absence of posed. deformity in the rheumatoid rheumatoid arthritis. Midfoot joint subluxation and arthritis midfoot. It is also seen Subluxation and dislocation dislocation are a characteristic fea- with neuropathic osteoarthropa- are frequently encountered in the ture of tarsal neuropathic os- thy. Alignment abnormalities are rheumatoid forefoot. These teoarthropathy. This change is es- not commonly observed with changes especially affect the less- pecially noteworthy at the tar- seronegative and gouty arthritis. er metatarsophalangeal joints. sometatarsal joints, although it Continued on page 198 The digits dislocate superiorly; can also occur at the in- superimposition of the proximal tertarsal joints (Figure phalanx base on the metatarsal 27). The forefoot dislo- head may appear as ankylosis in cates superolaterally rel- the dorsoplantar view (Figure 26). ative to the rearfoot. Metatarsophalangeal joint dislo- Posterosuperior cal- cation is best appreciated with caneal displacement is

Figure 26. Rheumatoid arthritis: Metatarsophalangeal joint Figure 27. Neuropathic osteoarthropathy: Midfoot dislocation simulating ankylosis. subluxation and dislocation. www.podiatrym.com APRIL/MAY 2004 • PODIATRY MANAGEMENT 197 Joint Disorders... erosion of the adjacent calcaneus the foot are the inferior calcaneal (Figure 28). The erosion may be tuberosities and the posterior cal- ContinuingRoentgen Features at Sites bounded by sclerosis in some in- caneus. The fifth-metatarsal Distant from Involved Joints stances. Retrocalcaneal bursitis Medical Education tuberosity is infrequently affected. caused by local trauma or irrita- Inferior calcaneal spur forma- Erosion tion should not in turn cause un- tion associated with degenerative With rheumatoid and seroneg- derlying bone pathology in the joint disease and rheumatoid ative arthritis, erosions may also absence of infection or systemic arthritis is generally well defined. be found at sites distant from in- inflammatory rheumatic disease. Degenerative spurs commonly are volved joints. The calcaneus is a Erosion along the inferior surface pointed and sometimes hook common location. The site most of the medial tuberosity can also shaped. However, early spur devel- frequently affected is the bursal be encountered. Rarely, calcaneal opment, regardless of etiology, projection (posterosuperior as- erosions are seen associated with may be ill defined. Calcaneal spur pect). The retrocalcaneal bursa lies gout. formation related to seronegative over this portion of bone. The Psoriatic arthritis can erode the arthritis tends to be large and ir- bursa is lined by synovium, and hallux ungual tuberosity. This regular. Ill-defined erosion and ad- the bursal projection is covered may be an isolated finding. The jacent sclerosis frequently accom- with cartilage.26 The bursitis ac- outline of the tuberosity appears pany these spurs (Figure 30). Infe- companying rheumatoid arthritis irregular and sometimes spiculat- rior calcaneal spurs may be seen and the seronegative arthritides ed (Figure 29). This finding alone with gout. They are smaller and ill frequently causes rarefaction and is not pathognomonic for psoriat- defined. ic arthritis: One variation of normal Soft Tissue Masses appears similar. Gouty tophi may be found anywhere in the foot, not just Enthesopathy intra- or periarticular. Rheumatoid Enthesopathy nodules are rarely encountered in represents an alter- radiographs of the foot but could ation at any liga- appear similarly at extra-articular mentous or ten- sites. donous attachment to bone (that is, en- Patterns of Joint Disease and thesis). It may pre- Distribution of Roentgen sent as spur forma- Findings tion, erosion, or a combination there- Joints involved of. Enthesopathy Each of the joint disorders Figure 28. Rheumatoid arthritis: Enthesopathy. has been associated consistently target specific sites in with many joint the foot. Furthermore, joints may disorders27 (Table be involved that are clinically 9). Common sites asymptomatic. Radiographs of of enthesopathy in Continued on page 199

Figure 30. Rheumatoid arthritis: Enthesopathy—spur and Figure 29. Psoriatic arthritis: Ungual tuberosity erosion. erosion (arrow).

198 PODIATRY MANAGEMENT • APRIL/MAY 2004 www.podiatrym.com MedicalContinuing Education Joint Disorders... EXAMINATION both feet (dorsoplantar and lateral views, at a mini- mum) are needed to assess the pattern of joint disease and distribution of roentgen findings. Table 10 lists the See instructions and answer sheet primary joints targeted by the more common pedal dis- on pages 246-248. orders. The patterns of joint involvement and distribution of roentgen findings are discussed in more detail 1) A joint disorder that can target the distal in- with the following characteristic descriptions of each terphalangeal joints of lesser toes is: joint disorder. A) osteoarthritis. Extra-Articular Sites Involved B) rheumatoid arthritis. The calcaneus is not an uncommon site of involve- C) psoriatic arthritis. ment associated with joint disease. Both spur and erosion may be encountered at inferior and retrocalcaneal D) gouty arthritis. locations. For this reason, lateral views should always be included with dorsoplantar views of the feet when 2) Erosions have a predilection for the medial evaluating for joint disease. It is unusual to see erosions of the calcaneus unless they are associated with inflam- aspects of all metatarsophalangeal joints and matory rheumatic disease or infection. Occasionally an the hallux interphalangeal joints in: erosion may be encountered with gouty arthritis at an A) gouty arthritis. enthesis, adjacent to a tophus. ■ B) psoriatic arthritis. References C) rheumatoid arthritis. 1 Rubin DA: The radiology of early arthritis, Semin D) osteoarthritis. Roentgenol 31(3):185, 1996. 2 Christman RA: A systematic approach for radiographically evaluating joint disease in the foot, J Am Podiatr Med Assoc 3) Periarticular osteopenia and subchondral re- 81(4):174, 1991. 3 Resnick D: The target area approach to articular disor- sorption, mixed with sclerosis, is frequently ders: a synopsis. In Resnick D, Niwayama G: Diagnosis of seen in the midfoot and tarsus, associated with bone and joint disorders, ed 2, p 1913, Philadelphia, 1988, Saunders. fragmentation and subluxation and/or disloca- 4 Forrester DM, Brown JC: The radiographic assessment of tion, in: arthritis: the plain film, Clin Rheum Dis 9(2):291, 1983. 5 Goldthwaite JE: The differential diagnosis and treatment of A) gouty arthritis. the so-called rheumatoid disease, Boston Med Surg J 151:529, B) rheumatoid arthritis. 1904. (Cited by Benedek TG, Rodnan GP: A brief history of the rheumatic diseases, Bull Rheum Dis 32(6):59, 1982.) C) neuropathic osteoarthropathy. 6 Edeiken J, Dalinka M, Karadick D: Edeiken’s roentgen di- D) psoriatic arthritis. agnosis of diseases of bone, ed 4, p 693, Baltimore, 1990, Williams & Wilkins. 7 Resnick D, Broderick TW: Bony proliferation of terminal 4) Normal joint space despite the presence of toe phalanges in psoriasis. The “ivory” phalanx, Can Assoc Ra- obvious periarticular erosion is characteristic of: diol J 28:187, 1977. 8 Martel W: The overhanging margin of bone: a roentgeno- A) gouty arthritis. logic manifestation of gout, Radiology 91:755, 1968. B) rheumatoid arthritis. 9 Kaye JJ: Arthritis: roles of radiography and other imaging techniques in evaluation, Radiology 177(3):601, 1990. C) osteoarthritis. 10 Barthelemy CR, Nakayama DA, Carrera GF et al: Gouty D) psoriatic arthritis. arthritis: a prospective radiographic evaluation of sixty patients, Skeletal Radiol 11:1, 1984. 11 Keil H: Rheumatic subcutaneous nodules and simulating 5) An overhanging margin of new bone at the lesions, Medicine 17:261, 1938. margin of an erosion is characteristic of: 12 Edeiken J, Dalinka M, Karadick D: Edeiken’s roentgen diagnosis of diseases of bone, ed 4, p 1369, Baltimore, 1990, A) rheumatoid arthritis. Williams & Wilkins. B) osteoarthritis. 13 Greenfield GB: Radiology of bone diseases, ed 4, p 688, Philadelphia, 1986, Lippincott. C) gouty arthritis. D) neuropathic osteoarthropathy. Dr. Christman is Director of Radiology and Assistant Pro- fessor at the Temple University School of Podiatric Medi- 6) An inflammatory, erosive joint disorder that is cine. He is Editor of Foot and Ankle Radiology (Churchill Livingstone, 2003) from which this CME has been reprint- associated with “whiskering” along the margin of ed (from pp. 482-96) with the kind permission of Elsevier Science. Continued on page 200 www.podiatrym.com APRIL/MAY 2004 • PODIATRY MANAGEMENT 199 Continuing EXAMINATION (cont’d) Medical Education

the hallux distal phalanx shaft is: tion disease (CPPD). 16) All of the following are sec- A) gouty arthritis. D) rheumatoid arthritis. ondary findings associated with B) rheumatoid arthritis. joint disease EXCEPT: C) psoriatic arthritis. 11) Periostitis is most character- A) soft tissue edema. D) osteoarthritis. istic of: B) calcification. A) psoriatic arthritis. C) alignment abnormality. 7) Osteophytes are the charac- B) gouty arthritis. D) erosion. teristic findings associated C) osteoarthritis. with: D) neuropathic arthropathy. 17) An example of a “degenera- A) neuropathic os- tive” pathologic joint disorder is: teoarthropathy. 12) Retrocalcaneal erosions are A) rheumatoid arthritis. B) gouty arthritis. characteristic of (choose the two B) osteoarthritis. C) psoriatic arthritis. best answers): C) septic arthritis. D) osteoarthritis. A) osteoarthritis. D) psoriatic arthritis. B) gouty arthritis. 8) This question has more than C) psoriatic arthritis. 18) A joint disorder that demon- one correct answer. Select all D) neuropathic arthropathy. strates bone production as its correct choices. One or more primary radiographic feature is: joints presenting with arthritis 13) Subchondral sclerosis is A) rheumatoid arthritis. mutilans (i.e., “penciling”, “whit- most characteristic of: B) osteoarthritis. tling”, etc.) can be seen in: A) psoriatic arthritis. C) septic arthritis. A) psoriatic arthritis. B) osteoarthritis. D) psoriatic arthritis. B) forefoot neuropathic os- C) rheumatoid arthritis teoarthropathy. (adult onset). 19) Periostitis is NOT character- C) rheumatoid arthritis. D) gouty arthritis. istic of: D) All of the above A) psoriatic arthritis. 14) A characteristic target area B) ankylosing spondylitis. 9) The ivory phalanx is most in the foot for gouty arthritis is C) Reiter’s syndrome. characteristic of: the ______joint. D) rheumatoid arthritis. A) gouty arthritis. A) first metarsal-cuneiform B) osteoarthritis. B) lesser toe distal interpha- 20) Lesser toe IPJ involvement is C) psoriatic arthritis. langeal rarely ever seen in: D) neuropathic arthropathy. C) first metatarsophalangeal A) osteoarthritis. D) fifth metatarsophalangeal B) gouty arthritis. 10) Periarticular soft tissue C) neuropathic os- swelling and tendon calcifica- 15) Bilateral, symmetrical involve- teoarthropathy. tions are characteristic features ment of all metatarsophalangeal D) rheumatoid arthritis. of: joints is most characteristic of: A) osteoarthritis. A) osteoarthritis. B) hyroxyapatite crystal de- B) gouty arthritis. SEE INSTRUCTIONS position disease (HADD). C) neuropathic os- AND ANSWER SHEET C) calcium pyrophosphate teoarthropathy. ON PAGES 246-248 dihydrate crystal deposi- D) rheumatoid arthritis.

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