New A Systematic Approach to Differentiating Joint Disorders · 2017. 5. 29. · thermore, gouty...

X-rays can be an importanttool in confirming your

diagnosis.

APRIL/MAY 2004 • PODIATRY MANAGEMENTwww.podiatrym.com 185

out question, osteoarthritis is themost common, primarily becauseof the mechanical wear and tearthat weight-bearing activit iesplace on cartilage. However, it is

not unusual for the inflammatoryrheumatic diseases (rheumatoidarthritis, psoriatic arthritis, anky-losing spondylitis, and Reiter’s

By Robert A. Christman, D.P.M.

Continued on page 186

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You may enroll: 1) on a per issue basis (at $17.50 per topic) or 2) per year, for the special introductory rate of $109 (yousave $66). You may submit the answer sheet, along with the other information requested, via mail, fax, or phone. In the nearfuture, you may be able to submit via the Internet.

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An answer sheet and full set of instructions are provided on pages 246-248.—Editor

ObjectivesAfter completing this mate-

rial the reader shall be able to:1) List the radiographic

criteria for systematicallyevaluating joints and jointdisease.

2) Define: joint effusion,arthritis mutilans, and en-thesopathy.

3) List common joint dis-orders that are associatedwith arthritis.

4) Explain the importanceof a lesion (erosion, for exam-ple) having either a well-defined or ill-defined margin.

5) List target areas in thefoot and calcaneus for com-mon arthritic disorders.

6) Distinguish betweenthe joint disorders (basedon radiographic findings).

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Several arthritides (types ofarthritis) have a predilectionfor the foot (Table 1). With-

A SystematicApproach to

DifferentiatingJoint Disorders







P O D I A T R I C R A D I O G R A P H YP O D I A T R I C R A D I O G R A P H Y

The archetypal radiographicpresentations of joint disordersthat have been described in theliterature are not necessarily whatthe clinician encounters in every-day practice. The classic picture istypically the patient who was di-agnosed with the joint diseasemany years or even decades ago.In contrast , the pat ient withacute symptomatology may ini-tially come for help at the onsetof disease or soon thereafter. Insuch a case, the radiographicfindings are frequently subtle andnonspecific, the clinical findingsare vague, and the diagnosis isoften elusive. Furthermore, atypi-cal cases are common. The chal-lenge, therefore, is to identify thesubtle, early radiographic find-ings, because the classic featuresof a particular joint disorder donot manifest until many yearslater. To maximize the detectionof early arthritis, you “must knowhow to look, where to look, andwhat to look for.”1 Then, alongwith the clinical and other labo-ratory findings, you must list and

consider the probable differentialdiagnoses.

Systematic Approach toDifferentiating Joint Disorders

A detailed, systematic ap-proach for evaluating pedal jointsentails three considerations2

(Table 2). For obvious reasons, thesymptomatic joint or joints are as-sessed first. The asymptomaticjoints of both extremities shouldalso be evaluated, for two reasons:Most joint disorders target bothextremities, and joints may be af-fected that are clinically asymp-tomatic. (Joint disease is one ofthe few conditions that warrantsperforming a bilateral radiograph-ic study.) The examination does-n’t stop here, however. Sites dis-tant from involved joints, osseousand soft tissue are also considered.Abnormal f indings at the cal-caneal entheses and heel pain, forexample, can be associated withjoint disease. Finally, the distribu-tion of radiographic findings mustbe assessed for specific patterns.3

Many articular disorders demon-strate characteristic patterns ofjoint involvement that help dis-tinguish one disease from another.

Articular disorders affectingthe foot may involve one or mul-tiple joints. Monoarticular jointdisease is generally attributed toeither trauma, infection, or acutegouty arthritis (Table 3). Less com-mon causes of pedal monoarticu-lar disease include rheumatoidmonoarthritis and pigmented vil-lonodular synovitis. Examples ofpolyarticular joint disorders affect-ing the foot include osteoarthritis,rheumatoid arthritis, seronegative


186 www.podiatrym.comPODIATRY MANAGEMENT • APRIL/MAY 2004

Joint Disorders...

syndrome) to first appear orbe diagnosed in the feet. Fur-

thermore, gouty arthritis and dia-betic neuropathic osteoarthropa-thy target have a predilection forthe foot.

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To maximize thedetection of early

arthritis, you “mustknow how to look,

where to look, and whatto look for.”

TABLE 1

Joint Disorders Affecting the Foot

Osteoarthritis Rheumatoid arthritis Psoriatic arthritis Reiter’s syndrome Ankylosing spondylitis Gouty arthritis Neuropathic osteoarthropathySeptic arthritis

TABLE 2

A Systematic Approach to EvaluatingJoint Disease

Roentgen features at or adjacent to involved joints Primary findings Osseous erosion New bone formation Joint space alteration Secondary findings Soft tissue edema Calcification Geographic rarefaction Alignment abnormalities Roentgen features at sites distant from involved joints Erosion Enthesopathy Soft tissue mass Patterns of joint disease according to distribution of roentgen findings Joints involved Targeted joints Bilateral versus unilateral Symmetry versus asymmetry

Extra-articular sites involved


ing pathologic processes:degenerative, inflamma-tory, and metabolic4

(Table 4). This classifica-tion, unfortunately, doesnot include neuropathicosteoarthropathy. In1904, Goldthwaite usedradiographic criteria todistinguish between os-teoarthritis and rheuma-toid arthritis.5 These crite-ria can be expanded toinclude the remainingforms of pedal arthritis.

Joint disorders affect-ing the foot can be divid-ed into two radiographiccategories, based on thepredominant radiograph-ic feature: hypertrophicand atrophic (Table 5).Hypertrophic joint dis-ease features bone over-growth and enlargement.The characteristic findings are sub-chondral sclerosis and osteophyte for-mation at the margin of a joint. Detri-tus arthritis, a subcategory of hyper-trophic arthritis, includes those disor-ders that exhibit fragmentation in ad-dition to exaggerated hypertrophicfeatures. The loss of bone substance,primarily through erosion, and jointspace narrowing, with or without pe-riarticular osteoporosis, characterize

arthritis (psoriatic arthritis, anky-losing spondylitis, and Reiter’s syn-drome), neuropathic osteoarthropa-thy, and chronic tophaceous gout.

Differentiation of joint disorderscan be simplified by applying a gener-al classification system to the present-ing features. One categorization ofarthritis has been based on underly-

the atrophic joint disor-ders. A subdivision of thisgroup is commonly associatedwith an adjacent soft tissue massclinically and the preservation ofjoint space. Forrester and Brown haveused the term “lumpy-bumpy” jointdisease to characterize this lattergroup..4

Neuropathic osteoarthropathy isdivided into two subtypes: forefoot,and the combined midfoot and tar-sus. Its radiographic features vary de-pending on location: Forefoot sitesexhibit findings characteristic of at-rophic joint disease; the midfoot andtarsal sites display features of detritus(hypertrophic) arthritis.

Each of the roentgen featuresassociated with joint disease is dis-cussed individually in the followingsections. Remember the radio-graphic categories of joint disor-ders; you can recognize associationsbetween certain roentgen findingsand arthritis categories, improvingyour diagnostic acumen.

Roentgen Features at InvolvedJoints: Primary Findings

Osseous ErosionBone erosion is a primary fea-

ture of all joint disorders excepthypertrophic joint disease. Gener-ally speaking, erosion associatedwith active atrophic joint diseaseappears small, ill defined, and ir-


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Figure 1. Irregular, ill-defined erosion (ankylosingspondylitis).

TABLE 3

Causes of Joint Disease

Monoarticular Trauma Infection

Crystal deposition Gout CPPD

Rheumatoid monoarthritisPigmented villonodular synovitis

PolyarticularOsteoarthritisRheumatoid arthritisSeronegative arthritisChronic tophaceous goutNeuropathic osteoarthropathyPigmented villonodular synovitis (midfoot)Multiple reticulohistiocytosis

TABLE 4

Categories ofJoint Disease

(based on underlying pathology)

DegenerativeOsteoarthritis

InflammatoryRheumatoid arthritisSeronegative arthritis

Psoriatic arthritis Reiter’s disease Ankylosing spondylitis

Septic arthritis Metabolic

Gouty arthritis

flammatory rheumatic disease inthe proper clinical setting. Thepresence of an erosion excludesosteoarthritis as a primary diagno-sis; however, both a trauma-in-duced subchondral bone defectand a subchondral bone cyst canmimic the appearance of an ero-sion (Figure 3).

Erosion is an early finding inthe course of an inflammatoryjoint disease. The erosions areintra -ar t icular and typica l lybegin along the medial or lateralmargins of the joint. Betweenwhere the cartilage ends and thejoint capsule inserts is a bonysurface covered only by perios-teum or perichondrium.3 Thissurface is in contact with thesynovium and its f luid and isknown as the “bare” area. The in-flamed synovium, known as pan-nus, invades the bone; on a ra-diograph, the outer margin ofsubchondral bone quickly disap-pears. Initially this disappearancemay be as subtle as a “dot-dash”appearance or “skipping” along

the thin white line that compris-es the subchondral bone plate(Figure 4). Eventually the local-



Joint Disorders...

regular (Figure 1). This char-acterization contrasts with the

larger, well-defined C-shaped ero-sion classically seen in the disor-ders associated with an adjacentsoft tissue mass (Figure 2). Erosionassociated with gouty arthritis,however, is indistinguishable earlyin the disease process, but preser-vation of joint space and target in-volvement of the first metatar-sophalangeal joint differentiategouty arthritis from the other in-

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Figure 3. Subchondral bone cyst mim-icking an erosion.

TABLE 5

Categories of Joint Disease (based on radiographic features)

Hypertrophic joint diseaseOsteoarthritisDetritus arthritis

Post-traumatic arthritisTarsus and midfoot neuropathic osteoarthropathy

Atrophic joint diseaseRheumatoid arthritisSeronegative arthritis

Psoriatic arthritisAnkylosing spondylitisReiter’s disease

Septic arthritisForefoot neuropathic osteoarthropathy

Associated with adjacent soft tissuemass and preservation of joint space

Gouty arthritisMultiple reticulohistiocytosisPigmented villonodular synovitis

TABLE 6

ArthritisMutilans

Figurative termsPencil-in-cup deformityMortar and pestleSucked candy stickWhittling

Differential diagnosisPsoriatic arthritisForefoot neuropathic osteoarthropathyRheumatoid arthritis (fifth metatarso-phalangeal joint)

Figure 2. Well-defined, C-shaped ero-sion (gouty arthritis).


ized loss of marginal bone (de-creased density) progresses so farthat the form of the af fectedbone appears abnormal. Thesefindings may be recognized daysor weeks after the onset of symp-toms and contribute to the ero-sion’s ill-defined and irregularappearance.

The well-defined erosion, incontrast, appears radiographicallyseveral months or years after theinitial onset of symptoms. It fre-quently results from chronic pres-

Joint Disorders...

TABLE 7

Forms of Bone Production andAssociated Joint Disorders

OsteophyteOsteoarthritis

Subchondral sclerosisOsteoarthritisNeuropathic osteoarthropathy (midfoot and tarsus)

PeriostitisSeronegative arthritisPsoriaticReiter’sSeptic arthritisForefoot neuropathic osteoarthropathy

Overhanging margin (Martel’s sign)Gouty arthritis

WhiskeringPsoriatic arthritis Ivory phalanxPsoriatic arthritis

TABLE 8

Grouping of Joint Disease Based onJoint Space Alteration

JOINT SPACE ARTHRITIS

Nonuniform narrowing Degenerative arthritis Uniform narrowing Inflammatory arthritis Normal or near normal joint space Miscellaneous arthritis

From Kaye JJ: Radiology 177(3):601, 1990.

Figure 4. Early rheumatoid arthritis:Dot-dash or skip pattern.

sure atrophy secondaryto direct apposition of asoft tissue mass with con-comitant infiltration and re-placement of bone (Figure 2). Itmay or may not be intra-articularin location. Or it may resultmonths or years after an acute, ill-defined erosion remodels.

Erosions that involve bothmargins of any metatarsopha-langeal or interphalangeal jointcan result in a condition known asarthritis mutilans. Arthritis muti-lans, also called resorptivearthropathy, is characterized byconcentric bone resorption andprimary joint destruction.4 Boneresorption may even expand to in-clude the nearby metadiaphysealcortex. This has figuratively beendescribed by several terms, mostcommonly the “pencil-in-cup” de-

formity. Other terms used to de-scribe arthritis mutilans are listedin Table 6. This presentation hascharacteristically been associatedwith psoriatic arthritis (Figure 5).However, forefoot neuropathic os-teoarthropathy and rheumatoidarthritis at the fifth metatarsopha-langeal joint (Figures 6 and 7) pre-sent similar pictures.

New Bone FormationThe predominant feature of

hypertrophic joint disease is boneproduction. Osteophytosis andsubchondral sclerosis are charac-teristic radiographic findings.Bone production, however, canshow other forms, including pe-riostitis, whiskering, and corticaland trabecular thickening. Thislatter group of examples is notseen with hypertrophic joint dis-ease but is frequently associated

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Hypertrophic jointdisease features bone

overgrowth andenlargement.

chondral sclerosisrepresents bone pro-duction and is not aprimary feature ofthe atrophic andsoft t issue erosivejoint disorders.

The presence ofperiostitis near themetaphysis of as y m p t o m a t i cmetatarsophalangealor interphalangealjoint is highly sug-gestive of seronega-tive arthritis (Figure9). Unfortunatelythe periostit is isshort-lived: Withina few weeks it quick-ly remodels and be-come continuouswith the bony mar-gin. Periostitis mayalso be seen withseptic arthritis andforefoot neuropathicosteoarthropathy.The latter disease isdifficult to differentiate from in-fection.

A variation of periostitis seenparticularly with psoriatic arthritisis referred to as “whiskering,” be-cause it resembles the stubble ofnew beardgrowth.6 Itsspiculated ap-pearance radi-ates awayfrom the bonemargin, and it

is characteristically seen at thehallux and, less frequently, thelesser-digit distal interphalangealjoints (Figure 10). Ill-defined scle-rosis accompanies this finding.Whiskering appears to represent

concomitantnew bonef o r m a t i o nand erosionat the capsu-lar and liga-mentous en-theses.

Occasion-ally the distalphalanx ofan affecteddigit becomesquite denseor scleroticrelative tonormal bonedensity. Thisis seen espe-cially in thehallux (Fig-ure 11).Known as the“ivory” pha-lanx, it is an-other presen-tation associ-


Joint Disorders...

with seronegative arthritis.New bone production is rarely

seen at joints affected by rheuma-toid arthritis. An overhangingmargin of new bone is frequentlyassociated with the C-shaped ero-sions encountered with goutyarthritis. Table 7 lists the varyingforms of bone production and as-sociated joint disorders.

An osteophyte is a spur at themargin of a joint (Figure 8). It is a

classic feature of osteoarthritis.Numerous figurative terms havebeen applied to this lesion, in-cluding dorsal flag (along the first-metatarsal head), lipping (if atboth sides of the joint) , andbeaking.

Subchondral sclerosis is alsoreferred to as eburnation (Figure8). It is, rarely, seen in the absenceof joint space narrowing. Sub-

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Figure 5. Arthritis mutilans: Psoriatic arthritis.Figure 6. Arthritis mutilans: Neuropathic os-teoarthropathy.

TABLE 9

Differential Diagnosis of Enthesopathy

in the Foot

Trauma Degenerative disease

OsteoarthritisDiffuse idiopathic skeletal hyperostosis

Inflammatory joint diseaseRheumatoid arthritisSeronegative arthritis

Crystal deposition diseaseCPPD (probable)HADD (probable)

Gout (possible) Endocrine disorders

Diabetes mellitus

Arthritis mutilans, alsocalled resorptivearthropathy, is

characterized byconcentric bone

resorption and primaryjoint destruction.

Cont’d on page 191


ated, in the proper clinical setting,with psoriatic arthritis.7

The well-defined erosions ofgouty arthritis occasionally havean overhanging margin of newbone (Figure 12). This finding, de-scribed by Martel8 represents newbone production at the margin ofan erosion. The body seems to beresponding to the presence of thetophus and attempting to encap-sulate it or wall itoff . The over-hanging marginof bone is not anuncommon find-ing. Its presencestrongly suggestsgouty arthrit is .Another findingsometimes associ-ated with the ero-sions of goutyarthrit is is sur-rounding sclero-sis.

Joint Space AlterationNormal, widened, or narrowed

joint spaces may be seen with ar-ticular disorders. Kaye has corre-lated the types of joint space alter-ation with three groups of arthri-tides9 (Table 8). This table, alongwith the remaining radiographicand clinical information, offersvaluable information that can leadto diagnosis of the arthritis inquestion.

Excess fluid accumulates in ajoint that is acutely inflamed. Toaccommodate this fluid, the cap-sule becomes stretched and theopposing bones are distracted. Ra-diographically this may appear aswidening of the joint space. Un-fortunately, joint space wideningsecondary to acute synovitis is avery subtle finding. Furthermore,the finding is short-lived; its ra-diographic presence is a hit-or-miss incident.

Extensive erosion of subchon-dral bone also gives the appear-ance of jo int space widening(Figure 13). Erosion and subse-quent fibrous tissue depositionbetween bones contribute to thewidening seen in psoriatic arthri-tis.2

The joint space seen radio-graphically corresponds to the car-tilage lining each bony surface.

Joint Disorders... Erosion or lysis of thearticular cartilage eventu-ally appears as joint spacenarrowing, as the two opposingsurfaces retract on one another.This is an early radiographic find-ing with inflammatory joint disor-ders such as rheumatoid or septicarthritis. Joint space narrowingmay be either even or uneven.The narrowing seen with inflam-

matory arthritisusually is evenor uniformacross the joint(Figure 14). Thisis because in-flammatory pan-nus is foundthroughout thejoint and affectsall cartilage. Incontrast, os-teoarthritis sec-ondary to wearand tear or trau-

ma usually only involves a seg-ment of the cartilage or subchon-dral bone, not the entire surface.As a result, narrowing of the jointspace has an uneven or nonuni-form presentation radiographical-ly (Figure 15). The unaffectedjoint segment has normal spacing.

The presence of a normal jointContinued on page 192

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Figure 9. Psoriatic arthritis: Periosti-tis.

Figure 7. Arthritis mutilans: Rheuma-toid arthritis (fifth-metatarsopha-langeal joint).

Figure 8. Osteoarthritis, f irstmetatarsophalangeal joint. Osteo-phytes (white arrows) and subchon-dral sclerosis (black arrows).

Excess fluid accumulates in a joint

that is acutely inflamed.

rectly involved until much later inthe course of disease. As a result,the presence of normal joint spacein light of obvious erosion is acharacteristic finding. This is in

strict contrast toi n f l a m m a t o r yjoint disease. Theaggressive natureof this lattergroup of disor-ders and associ-ated intense syn-ovitis quiterapidly causebone and carti-lage destruction.

Bony or fi-brous ankylosismay occur be-tween two jointsurfaces as an end

stage of some joint diseases. This isespecially true of the inflammatoryjoint disorders. Bony ankylosis ismore commonly associated withseronegative arthritis and septicarthritis. The interphalangeal joints

are targeted in psoriatic arthritis.Midfoot ankylosis may be seen inthe rheumatoid foot (Figure 17).Ankylosis is seldom seen withgouty arthritis and is not associatedwith pedal osteoarthritis. However,the superimposition of osteophytesand joint space narrowing maysimulate bony ankylosis.

Roentgen Features at InvolvedJoints: Secondary Findings

Soft Tissue Edema and MassesSoft tissue edema may be gen-

eralized throughout the foot, re-gional, or localized to a joint or

other site. It is viewed radiograph-ically as an increased soft tissuedensity and/or volume relative tonormal expectation. Generalizedsoft tissue edema can be related toabnormal systemic conditions(cardiac disease, acromegaly), dif-fuse inflammatory states (celluli-tis), or peripheral vascular disease(venous insufficiency, lymphede-ma).4 It is not, however, a primaryfinding in joint disorders. Manypatients with pedal joint diseasehave concomitant generalized softtissue edema that is secondary tothe conditions just noted.

Regional soft tissue edema isconfined to a smaller segment ofthe body. An entire digit, for ex-ample, may be edematous fromacute inflammatory conditionsincluding infection, seronegativearthritis (the so-called sausagetoe), and gout. The edema associ-ated with an acute gouty attack atthe f i rst metatarsophalangealjoint may extend to the midfoot.This clinical presentation maycertainly mimic an infectiousprocess. Post-traumatic states alsocan show regional soft t i ssueedema. Neuropathic os-teoarthropathy of the midfootand tarsus shows either regionalor diffuse edema.

Localized soft tissue edemamay be related to synovial inflam-mation or to a mass. The edemaassociated with synovitis sur-rounds the joint and is quite well



Joint Disorders...

space associated with periar-ticular erosion is characteristic

of joint disorders associated withsoft tissue masses(Figure 16).Chronic topha-ceous gout, forexample, is notprimarily an in-flammatory dis-order. Althoughintense inflam-mation is clini-cally seen withacute attacks ofgout, these symp-toms last only ashort period oftime. Severalyears may lapsebefore radiographic evidence ofjoint disease is evident. Further-more, many of the erosions associ-ated with gouty arthritis are peri-articular, outside the capsule.Therefore cartilage may not be di-

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Figure 11. Psoriatic arthritis: Ivoryphalanx.

Figure 12 Gouty arthritis: Martel’ssign.

Figure 10. Psoriatic arthritis: Whiskering at hallux.

Increased soft tissuedensity and volume

secondary to synovitis is known as

joint effusion.


Periarticular soft tissue massesare associated with a few joint dis-orders. The most common exam-ple is the gouty tophus. Tophi arewell-defined masses that are foundadjacent to joints or at extra-artic-ular sites (Figure18). They occa-sionally exhibitcalcification (seefollowing discus-sion). Lesions aredistributed asym-metrically in thefoot.

Tophi may beseen several yearsafter the initialonset of symp-

t o m s .They area charac-teristic feature of chronictophaceous gout and mayor may not be associatedwith erosions; the latterdevelop adjacent to tophi.It has been reported thatthe clinical presence oftophi are strongly associ-ated with the characteris-tic radiographic featuresof gouty arthritis.10

Another soft tissue ero-sive joint disorder is mul-tiple reticulohistiocytosis.These masses radiographi-cally appear similar tothose seenin gout.

defined radiographically. In-creased soft tissue density and vol-ume secondary to synovitis isknown as joint effusion. This con-dition, although nonspecific, ishighly associated with inflamma-tory joint disease. However, syn-ovitis secondary to trauma, eitheracute or chronic and repetitive,appears radiographically identicalto that caused by inflammatoryrheumatic disease (rheumatoidand seronegative arthritis). Inacute attacks of gout, the edema ispronounced. It often mimics thediffuse edema associated with in-fection.

Joint Disorders... However, masses associ-ated with multiple reticu-lohistiocytosis are wide-spread, symmetric, and noncal-cifying.

Soft tissue masses are occasion-ally seen withr h e u m a t o i da r t h r i t i s .R h e u m a t o i dnodules are sel-dom found inthe foot but,when present,may radiographi-cally appear in-distinguishablefrom a gouty to-phus except thatthe former rarelycalcifies.11

Soft tissue tu-mors and tumor-like lesions maymanifest in periarticular locationsand cause articular erosions. Al-though not common, an exampleof one such lesion occurring inthe foot is pigmented villonodularsynovitis. As a rule, it is monoar-ticular. However, a rare, polyartic-ular manifestation can appear inthe midfoot (Figure 19). This isprobably related to the uniquesynovial compartmentalization inthis anatomic region. Well-de-fined erosions develop adjacent tosoft tissue masses.


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Figure 14. Rheumatoid arthritis: Even joint space narrow-ing.

Figure 15. Osteoarthritis: Uneven joint space narrow-ing.

Figure 13. Psoriatic arthritis: Joint space widen-ing secondary to erosion.

In the foot, radiographic

visualization of calcifiedcrystals is best

appreciated in theperiarticular soft

tissues.

ic. Dystrophic calcifications occurin soft tissues that are damagedor altered but have no underlyingdisturbance in calcium or phos-phorus metabolism.12,13

So f t t i s sue ca lc i f i ca t ions ,when associated with joint dis-ease, may be diagnostic for agroup of disorders known as thecrystal deposition diseases. Theyare monosodium urate crystaldeposition disease (gouty arthri-tis), calcium pyrophosphate di-hydrate (CPPD) deposition dis-ease, and hydroxyapatite crystaldeposition disease (HADD). Cal-cifications can be found in theperiarticular tissues, joint cap-sule, or cartilage.

The crystals associated withgouty arthritis may be deposited

in the joint capsule, syn-ovium, cartilage, subchon-dral bone, or periarticulartissues.14 A collection ofmonosodium urate crystalsin the soft tissues is knownas a tophus. In the foot, ra-diographic visualization ofcalcified crystals is best ap-preciated in the periarticu-lar soft tissues.

Tophus calcification isoccasionally seen withtophaceous gout. Althoughnot a pathognomonic find-ing, calcification of a peri-articular soft tissue mass,especially if situated adja-cent to an erosion, is high-ly suggestive of gouty



Figure 17. Bony ankylosis. A, Psoriatic arthritis. B, Rheumatoid arthritis.

Figure 18. Gout: Tophus at hallux in-terphalangeal joint.

Figure 16. Gout: Sparing of jointspace despite erosive disease.

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, distalinterphalangeal joint.

A B

Joint Disorders...

CalcificationNumerous disorders are asso-

ciated with soft tissue calcifica-tion in the foot. Widespread softtissue calcification in otherwisenormal tissues is associated withdisorders that demonstrate ele-vated calcium or phosphate levelsin the serum. Hyperparathy-roidism, for example, may causediffuse periarticular, capsular,and vessel calcification. The ma-jority of soft tissue calcificationsseen in the foot, however, areprobably dystrophic or idiopath-

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findings are known as pyrophos-phate arthropathy when associat-ed with CPPD deposition. Calcifi-cations can occur in articular andperiarticular soft tissues. However,cartilage calcification, or chondro-

calcinosis, has re-ceived the most atten-tion. The primary crys-tal associated withchondrocalcinosis ap-pears to be CPPD.

Little has been re-ported in the literatureregarding pedal CPPDinvolvement. Perhapsthis is because micro-scopic examination forcrystals is not per-formed routinely forthe workup of acutelysymptomatic joints.However, the litera-ture refers to metatar-sophalangeal, tarsal,and ankle joint in-volvement.16 Chondro-calcinosis is not readi-ly recognized at thetarsal joints, because

other bones are superimposed.Magnification radiographyusing high-detail industrialx-ray film may be neces-sary to see the subtlemetatarsophalangeal jointcalcifications.17

Calcification of periar-ticular structures, includ-ing tendons and bursae, isalso seen with hydroxyap-atite crystal deposition dis-ease (HADD).18 The clinicalcourse may mimic the sin-gle-joint symptomatologyseen with gout and pseudo-gout.19 The radiographicpresentation of HADD, alsoreferred to as calcifyingtendonitis , consists ofround or oval calcificationswithin the course of a ten-don.20 Linear or punctate calcificdensities may be seen along themargins of affected joints. Anoth-er presentation can be a ratherlarge, amorphous calcification ad-jacent to a joint.

Calcifications and ossificationsmay be seen in the joint itself andare referred to as loose bodies.Loose osseous bodies (“jointmice”) vary considerably in size

arthritis in the proper clinical set-ting. Small, punctate calcificationscan be identified in the soft tissuemass (Figure 20).

Calcium pyrophosphate dihy-drate (CPPD) deposition disease isassociated with several patterns ofjoint involvement.15 In general, ra-diographic features include softtissue calcification, joint spacenarrowing, subchondral sclerosis,and fragmentation. The latter

Joint Disorders... and architecture. Theyare not uncommon in os-teoarthritic joints (Figure21). Trauma can cause osteo-phytes or subchondral bone withoverlying cartilage to break off.These fragments of bone and/orcarti lage can float or becomewedged within the joint or syn-

ovium. Because many of theseloose bodies contain cartilage,faint calcifications may be identi-fied. They tend to enlarge overtime. Large osseous bodies or frag-ments and concomitant severe hy-

pertrophic joint disease in tarsaljoints are suggestive of eitherpost-traumatic arthritis or neuro-pathic osteoarthropathy (Figure22).

Geographic RarefactionSubchondral bone cysts occa-

s ional ly accompany arthrit is .They appear as geographic, lytic


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Figure 20. Gout: Calcified tophus.

Figure 21. Loose bodies.

Figure 19. Pigmented villonodular synovitis, tarsus.

Monosodium uratecrystals, typically

deposited in the softtissues in patients with

gout, may also bedeposited in bone.

thought to be pannus invadingthe subchondral bone.24

Monosodium urate crystals,typically deposit-ed in the soft tis-sues in patientswith gout, mayalso be depositedin bone. 25 Thisdeposit ion hasbeen associatedwith chronictophaceous gout.Multiple focal ,geographic areasof bone loss (rar-efaction) are seenat these sites (seeFigure 16). I haveobserved in a retrospective studyof a large group of patients thatlocalized rarefaction at the first

m e t a t a r -s o p h a -l a n g e a ljoint withthe absenceof erosionis frequent-ly an earlyradiograph-ic f indingin goutya r t h r i t i s .The rarefac-t ion is lo-

calized in the medial and superioraspects of the first-metatarsalhead (Figure 24). Although this

finding is non-specif ic, in theproper cl inicalsett ing it sug-gests goutyarthritis.

Alignment Ab-normalities

Positional de-formities may bee n c o u n t e r e dwith joint disor-ders. Abnormali-ties range fromnonspecific mis-

alignment of two bones to sublux-ation and dislocation.

A finding commonly associat-ed with rheumatoid arthritis isfibular deviation of the digits, es-pecially the hallux (Figure 25A).This finding generally does not in-volve the fifth digit, however. Theconstraints of shoe gear probablyprevent lateral deviation of thistoe. Erosion may or may not ac-company misalignment. Digitaldeviation in a fibular direction isnot found in all instances ofrheumatoid arthritis. Tibial devia-tion may also be encountered (Fig-



Joint Disorders...

lesions and may mimic ero-sions viewed en face. This is

especially true along the medialaspect of the f i rs t -metatarsalhead. The typical subchondralcyst with sclerotic margin is com-monly associated with degenera-tive joint disease21 (see Figures 3& 15). Its pathogenesis is contro-versial; the two probable mecha-nisms are bone contusion22 andsynovial intrusion.23 Subchondralcystic lesions have also been asso-ciated with rheumatoid arthritis(Figure 23). They have been re-ferred to as pseudocysts. Their ra-diographic appearance is identi-cal to the degenerative cyst butlacks a sclerotic margin.17 Themechanism of formation is

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

Figure 22. Detritus arthritis: Tarsal neuropathic osteoarthropathy.

Subluxation anddislocation are

frequently encounteredin the rheumatoid

forefoot.


the lateral view, although it isdifficult to visualize the jointstructures because the adjacentosseous structures are superim-posed.

Midfoot joint subluxation anddislocation are a characteristic fea-ture of tarsal neuropathic os-teoarthropathy. This change is es-pecially noteworthy at the tar-sometatarsal joints, although itcan also occur at the in-tertarsal joints (Figure27). The forefoot dislo-cates superolaterally rel-ative to the rearfoot.Posterosuperior cal-caneal displacement is

ure 25B). It is important to notethat hallux abductovalgus andlesser-toe deformities are nonspe-cific; these abnormalities are fre-quently seen in the absence ofrheumatoid arthritis.

Subluxation and dislocationare frequently encountered in therheumatoid forefoot . Thesechanges especially affect the less-er metatarsophalangeal joints.The digits dislocate superiorly;superimposition of the proximalphalanx base on the metatarsalhead may appear as ankylosis inthe dorsoplantar view (Figure 26).Metatarsophalangeal joint dislo-cation is best appreciated with

n o t e dwhen thet a l o c a l -caneal jointis involved.

Misalign-ment be-tween twoarticular sur-faces can re-sult in carti-lage damageand subse-quent os-teoarthritis.Examples in-clude halluxabductoval-g u s a n d

other medial column misalign-ments associated with pes planusand pes cavus.

Pes planovalgus is a frequentdeformity in the rheumatoidarthritis midfoot. It is also seenwith neuropathic osteoarthropa-thy. Alignment abnormalities arenot commonly observed withseronegative and gouty arthritis.


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Figure 26. Rheumatoid arthritis: Metatarsophalangeal jointdislocation simulating ankylosis.

Figure 27. Neuropathic osteoarthropathy: Midfootsubluxation and dislocation.

A BFigure 25. Rheumatoid arthritis. A, Fibular deviation. B, Tibial deviation. (Courtesy Irwin Juda, D.P.M.,Philadelphia)

erosion of the adjacent calcaneus(Figure 28). The erosion may bebounded by sclerosis in some in-stances. Retrocalcaneal bursitiscaused by local trauma or irrita-tion should not in turn cause un-derlying bone pathology in theabsence of infection or systemicinflammatory rheumatic disease.Erosion along the inferior surfaceof the medial tuberosity can alsobe encountered. Rarely, calcanealerosions are seen associated withgout.

Psoriatic arthritis can erode thehallux ungual tuberosity. Thismay be an isolated finding. Theoutline of the tuberosity appearsirregular and sometimes spiculat-ed (Figure 29). This finding aloneis not pathognomonic for psoriat-

ic arthrit is : Onevariation of normalappears similar.

EnthesopathyEnthesopa thy

represents an alter-ation at any liga-mentous or ten-donous attachmentto bone (that is, en-thesis). It may pre-sent as spur forma-tion, erosion, or acombination there-of. Enthesopathyhas been associatedwith many jointdisorders27 (Table9). Common sitesof enthesopathy in

the foot are the inferior calcanealtuberosities and the posterior cal-caneus. The f ifth-metatarsaltuberosity is infrequently affected.

Inferior calcaneal spur forma-tion associated with degenerativejoint disease and rheumatoidarthritis is generally well defined.Degenerative spurs commonly arepointed and sometimes hookshaped. However, early spur devel-opment, regardless of etiology,may be ill defined. Calcaneal spurformation related to seronegativearthritis tends to be large and ir-regular. Ill-defined erosion and ad-jacent sclerosis frequently accom-pany these spurs (Figure 30). Infe-rior calcaneal spurs may be seenwith gout. They are smaller and illdefined.

Soft Tissue MassesGouty tophi may be found

anywhere in the foot, not justintra- or periarticular. Rheumatoidnodules are rarely encountered inradiographs of the foot but couldappear similarly at extra-articularsites.

Patterns of Joint Disease andDistribution of RoentgenFindings

Joints involvedEach of the joint disorders

consistently target specific sites inthe foot. Furthermore, joints maybe involved that are clinicallyasymptomatic. Radiographs of


Joint Disorders...

Roentgen Features at SitesDistant from Involved Joints

ErosionWith rheumatoid and seroneg-

ative arthritis, erosions may alsobe found at sites distant from in-volved joints. The calcaneus is acommon location. The site mostfrequently affected is the bursalprojection (posterosuperior as-pect). The retrocalcaneal bursa liesover this portion of bone. Thebursa is lined by synovium, andthe bursal projection is coveredwith cartilage.26 The bursitis ac-companying rheumatoid arthritisand the seronegative arthritidesfrequently causes rarefaction and

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Figure 30. Rheumatoid arthritis: Enthesopathy—spur anderosion (arrow).

Figure 28. Rheumatoid arthritis: Enthesopathy.

Figure 29. Psoriatic arthritis: Ungual tuberosity erosion.



both feet (dorsoplantar and lateral views, at a mini-mum) are needed to assess the pattern of joint diseaseand distribution of roentgen findings. Table 10 lists theprimary joints targeted by the more common pedal dis-orders. The patterns of joint involvement and distribu-tion of roentgen findings are discussed in more detailwith the following characteristic descriptions of eachjoint disorder.

Extra-Articular Sites InvolvedThe calcaneus is not an uncommon site of involve-

ment associated with joint disease. Both spur and ero-sion may be encountered at inferior and retrocalcaneallocations. For this reason, lateral views should alwaysbe included with dorsoplantar views of the feet whenevaluating for joint disease. It is unusual to see erosionsof the calcaneus unless they are associated with inflam-matory rheumatic disease or infection. Occasionally anerosion may be encountered with gouty arthritis at anenthesis, adjacent to a tophus. ■

References1 Rubin DA: The radiology of early arthritis, Semin

Roentgenol 31(3):185, 1996.2 Christman RA: A systematic approach for radiographical-

ly evaluating joint disease in the foot, J Am Podiatr Med Assoc81(4):174, 1991.

3 Resnick D: The target area approach to articular disor-ders: a synopsis. In Resnick D, Niwayama G: Diagnosis ofbone and joint disorders, ed 2, p 1913, Philadelphia, 1988,Saunders.

4 Forrester DM, Brown JC: The radiographic assessment ofarthritis: the plain film, Clin Rheum Dis 9(2):291, 1983.

5 Goldthwaite JE: The differential diagnosis and treatment ofthe so-called rheumatoid disease, Boston Med Surg J 151:529,1904. (Cited by Benedek TG, Rodnan GP: A brief history of therheumatic diseases, Bull Rheum Dis 32(6):59, 1982.)

6 Edeiken J, Dalinka M, Karadick D: Edeiken’s roentgen di-agnosis of diseases of bone, ed 4, p 693, Baltimore, 1990,Williams & Wilkins.

7 Resnick D, Broderick TW: Bony proliferation of terminaltoe phalanges in psoriasis. The “ivory” phalanx, Can Assoc Ra-diol J 28:187, 1977.

8 Martel W: The overhanging margin of bone: a roentgeno-logic manifestation of gout, Radiology 91:755, 1968.

9 Kaye JJ: Arthritis: roles of radiography and other imagingtechniques in evaluation, Radiology 177(3):601, 1990.

10 Barthelemy CR, Nakayama DA, Carrera GF et al: Goutyarthritis: a prospective radiographic evaluation of sixty pa-tients, Skeletal Radiol 11:1, 1984.

11 Keil H: Rheumatic subcutaneous nodules and simulatinglesions, Medicine 17:261, 1938.

12 Edeiken J, Dalinka M, Karadick D: Edeiken’s roentgen di-agnosis of diseases of bone, ed 4, p 1369, Baltimore, 1990,Williams & Wilkins.

13 Greenfield GB: Radiology of bone diseases, ed 4, p 688,Philadelphia, 1986, Lippincott.

Joint Disorders...

1) A joint disorder that can target the distal in-terphalangeal joints of lesser toes is:

A) osteoarthritis.B) rheumatoid arthritis.C) psoriatic arthritis.D) gouty arthritis.

2) Erosions have a predilection for the medialaspects of all metatarsophalangeal joints andthe hallux interphalangeal joints in:

A) gouty arthritis.B) psoriatic arthritis.C) rheumatoid arthritis.D) osteoarthritis.

3) Periarticular osteopenia and subchondral re-sorption, mixed with sclerosis, is frequentlyseen in the midfoot and tarsus, associated withfragmentation and subluxation and/or disloca-tion, in:

A) gouty arthritis.B) rheumatoid arthritis.C) neuropathic osteoarthropathy.D) psoriatic arthritis.

4) Normal joint space despite the presence ofobvious periarticular erosion is characteristic of:

A) gouty arthritis.B) rheumatoid arthritis.C) osteoarthritis.D) psoriatic arthritis.

5) An overhanging margin of new bone at themargin of an erosion is characteristic of:

A) rheumatoid arthritis.B) osteoarthritis.C) gouty arthritis.D) neuropathic osteoarthropathy.

6) An inflammatory, erosive joint disorder that isassociated with “whiskering” along the margin of

See instructions and answer sheet on pages 246-248.

E X A M I N A T I O N

Dr. Christman is Director of Radiology and Assistant Pro-fessor at the Temple University School of Podiatric Medi-cine. He is Editor of Foot and Ankle Radiology (ChurchillLivingstone, 2003) from which this CME has been reprint-ed (from pp. 482-96) with the kind permission of ElsevierScience.

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tion disease (CPPD).D) rheumatoid arthritis.

11) Periostitis is most character-istic of:

A) psoriatic arthritis.B) gouty arthritis.C) osteoarthritis.D) neuropathic arthropathy.

12) Retrocalcaneal erosions arecharacteristic of (choose the twobest answers):

A) osteoarthritis.B) gouty arthritis.C) psoriatic arthritis.D) neuropathic arthropathy.

13) Subchondral sclerosis ismost characteristic of:

A) psoriatic arthritis.B) osteoarthritis.C) rheumatoid arthritis(adult onset).D) gouty arthritis.

14) A characteristic target areain the foot for gouty arthritis isthe ______________ joint.

A) first metarsal-cuneiformB) lesser toe distal interpha-langealC) first metatarsophalangealD) fifth metatarsophalangeal

15) Bilateral, symmetrical involve-ment of all metatarsophalangealjoints is most characteristic of:

A) osteoarthritis.B) gouty arthritis.C) neuropathic os-teoarthropathy.D) rheumatoid arthritis.

the hallux distal phalanx shaft is:A) gouty arthritis.B) rheumatoid arthritis.C) psoriatic arthritis.D) osteoarthritis.

7) Osteophytes are the charac-teristic findings associatedwith:

A) neuropathic os-teoarthropathy.B) gouty arthritis.C) psoriatic arthritis.D) osteoarthritis.

8) This question has more thanone correct answer. Select allcorrect choices. One or morejoints presenting with arthritismutilans (i.e., “penciling”, “whit-tling”, etc.) can be seen in:

A) psoriatic arthritis.B) forefoot neuropathic os-teoarthropathy.C) rheumatoid arthritis.D) All of the above

9) The ivory phalanx is mostcharacteristic of:

A) gouty arthritis.B) osteoarthritis.C) psoriatic arthritis.D) neuropathic arthropathy.

10) Periarticular soft tissueswelling and tendon calcifica-tions are characteristic featuresof:

A) osteoarthritis.B) hyroxyapatite crystal de-position disease (HADD).C) calcium pyrophosphate dihydrate crystal deposi-

16) All of the following are sec-ondary findings associated withjoint disease EXCEPT:

A) soft tissue edema.B) calcification.C) alignment abnormality.D) erosion.

17) An example of a “degenera-tive” pathologic joint disorder is:

A) rheumatoid arthritis.B) osteoarthritis.C) septic arthritis.D) psoriatic arthritis.

18) A joint disorder that demon-strates bone production as itsprimary radiographic feature is:

A) rheumatoid arthritis.B) osteoarthritis.C) septic arthritis.D) psoriatic arthritis.

19) Periostitis is NOT character-istic of:

A) psoriatic arthritis.B) ankylosing spondylitis.C) Reiter’s syndrome.D) rheumatoid arthritis.

20) Lesser toe IPJ involvement israrely ever seen in:

A) osteoarthritis.B) gouty arthritis.C) neuropathic os-teoarthropathy.D) rheumatoid arthritis.

E X A M I N A T I O N(cont’d)

SEE INSTRUCTIONSAND ANSWER SHEETON PAGES 246-248

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