Annals of the Rheumatic Diseases 1995; 54: 263-268

Joint space width measures cartilage thickness inosteoarthritis of the knee: high resolution plainfilm and double contrast macroradiographicinvestigation

J Christopher Buckland-Wright, Diana G Macfarlane, John A Lynch, M Kris Jasani,Charles R Bradshaw

AbstractObjective-To test reliability ofjoint spacewidth (JSW) measurements as a predictorof cartilage thickness in knees of patientswith osteoarthritis (OA), using highdefinition microfocal radiography.Method-JSW was measured from weightbearing plain film macroradiographstaken in the tunnel view and comparedwith the sum of femoral and tibialcartilage thicknesses measured fromdouble contrast macroarthrograms of thesame regions of the same knees obtainedin the non-weight bearing lateralposition.Results-All knees had medial compart-ment OA. Comparison oftheJSW with thesum of the tibial and femoral cartilagethicknesses revealed a highly significantcorrelation (p < 00001) between the twomeasurements in the medial but not thelateral compartment. In the middle regionof both compartments, JSW was smallerthan the cartilage thickness, indicatingthat, on standing, the curvature of thefemoral condyles compressed thecartilage in this region.Conclusions-JSW reliably measuredcartilage thickness in the medial but notthe lateral compartment of knees withmedial compartment OA. Dependingupon the stage ofOA disease, JSW reliablyreflects cartilage thinning and com-pression.

(Ann Rheum Dis 1995; 54: 263-268)

Joint space width (JSW) measurement is usedas a major criterion in the diagnosis ofosteoarthritis (OA) from radiographs and formonitoring progression of the disease.' Doubthas been cast on the reliability of this approachby studies in which the radiographic status ofthe joint was compared with the arthroscopicappearance of the cartilage surface.2 Theinvestigators found that joint space oftenappeared normal in patients who had severecartilage loss, or narrowed in knees withnormal cartilage.2 3 Recently, we have formallyevaluated the usefulness of the standingsemiflexed and weight bearing or modifiedtunnel view for the detection of joint spacenarrowing in patients with knee OA.4 Three

patterns of joint space narrowing wereevaluated, as observed in both views (30%), inonly the standing semiflexed view (8%), and inonly the weight bearing tunnel view (22%).The aim of this study was to verify if JSW

in the weight bearing tunnel view reliablymeasures cartilage thickness in OA. Instead ofusing arthroscopy, which mainly visualises thesurface appearance of cartilage, we undertooka double contrast radiographic study tovisualise and measure the thickness of thetissue from high definition macroradio-graphs.5 6 Compared with conventional radio-graphy, which has been shown to have a fairlylarge coefficient of variation for JSWmeasurement,7 8 macroradiography providesaccurate and reproducible measurements of xray features based on standardised radio-graphic and mensural procedures.5 6 8JSW was measured from plain film macro-

radiographs taken in the weight bearing ormodified tunnel view. It was compared withthe sum of the tibial and femoral cartilagethicknesses measured from double contrastmacroarthrograms of the same knee radio-graphed at the same angle but in the non-weight bearing lateral position. Initially,macroradiographs were obtained in the weightbearing tunnel position for such comparisons,but the procedure was abandoned as it resultedin the appearance of a fluid level in the joint,rendering it impossible to recognise thecartilage boundaries for purposes of thicknessmeasurements.

Patients and methodsPATIENTSWe studied 20 patients (six male) with a meanage of 58- 1 (range 35-74) years, a meandisease duration (based on the pain in theworst, most painful knee) of 5-7 (range 3-20)years, and a mean weight of 73-4 (range54-104) kg. Patient selection was based uponclinical and radiographic criteria. The status ofthe study knee was graded using the Kellgrenand Lawrence criteria.9 Exclusion criteriaincluded evidence of other types of arthritis,previous trauma, surgical intervention, ortreatment with corticosteroids. All patientswere seronegative for rheumatoid factor andhad an erythrocyte sedimentation rate withinthe normal range.

Division ofAnatomyand Cell Biology,United Medical andDental Schools, Guy'sHospital, London SEI9RT, United KingdomJ C Buckland-WrightJ A LynchDepartment ofRheumatology, Kentand Sussex Hospital,Tunbridge Wells, Kent,United KingdomD G MacfarlaneDepartment ofDiagnostic Radiology,Guy's Hospital,London SEl 9RT,United KingdomC R BradshawClinical Research,Ciba GeigyCorporation, Summit,New Jersey, USAM K Jasani (retired)Correspondence to:Dr J C Buckland-Wright.Accepted for publication31 October 1994

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As ethical considerations precludedsubjecting non-diseased age and sex matchedhospital attendees to radiography, macroradio-graphs of 14 healthy, non-arthritic volunteers(seven men and seven women, mean age 35-5(range 23-56) years; mean weight 73-2 (range60-89) kg) were obtained from medical andlaboratory staff. Radiographically, the knees ofall reference subjects were devoid of bothosteophytes and sclerosis. The dimensions oftheir joint space width provided a referencerange for the distance between bones inanatomically normal healthy knee joints ofsubjects with a body weight similar to that ofthe patients. These JSW data are referred to asthe reference values and were used to definethe degree to which JSW was narrowed in theOA knees. The difference in the mean age, ofapproximately 20 years, between the referencesubjects and OA patients might result in somejoint space loss in the latter, due to age.Whether age related changes are significantbetween the groups in this study, remainsspeculative since significant changes have beenreported only in studies in which the ages ofthesubjects were between 10 and 86 years andbetween 22 and 78 years.'01

PLAIN FILM MACRORADIOGRAPHY IN THE

WEIGHT BEARING TUNNEL VIEW

Stereopair macroradiographs at X5 magnifi-cation5 6were taken of the most painful knee-that is, the one selected for the arthrographicinvestigation. The knee was radiographed at1300 angle in the weight bearing or modifiedtunnel view,4 12 which involved the patientsitting on the edge of a stool with weighttransmitted through the leg undergoing x rayexamination. The joint was radiographed inthe anteroposterior position with the patient'sfoot placed in a slot on the patient table.4 12The 130° angle of flexion used in this study isthe same as that used for obtaining theconventional non-weight bearing tunnelview.'314 This angle was checked by means ofa Perspex template. With the aid of the laserand image intensifier screening, the position of

Figure1 Plain film macroradiograph ofan osteoarthnitic knee in the load bearing tunnelview showing the position in which thejoint was radiographed at XS magnification.Horizontal bar represents 41 mm.

the knee was adjusted to ensure that the tibialplateau was horizontal and perpendicular tothe radiographic plate and that the tibial spineswere centrally placed relative to the femoralnotch (fig 1). The view assessed alteration tocartilage thickness over the popliteal surface ofthe condyles.

DOUBLE CONTRAST MACROARTHROGRAPHY IN

THE NON-WEIGHT BEARING LATERAL POSITION

Niopam 200 (E Merck Ltd, Hampshire, UK)was chosen as the contrast medium for thearthrographic examination, as an earlierstudy'5 had shown that a contrast mediumcontaining iodine 200 mg/ml provided betterdefinition of the articular cartilage inmacroradiographs of the knee than contrastmedia with the greater iodine concentrationsused conventionally.

After injection of a local anaesthetic, fluidfound in the joint was aspirated. Five to 10 mlof the contrast medium was injected into thejoint cavity, followed by 40-80 ml of air. Abandage was then wrapped tightly around theleg immediately above the patella in order torestrict both medium and air from entering thesuprapatellar pouch. After injection of thecontrast medium and air, the knee was flexedand extended several times to spread themedium over the inner surface of the joint.This process was further aided by the patientwalking from the examination bed to the x rayunit.For radiography, the patient lay on the table

in the lateral position with the joint space to beexamined uppermost. By flexing the knee to1300 the joint space was spread open to displaythe intra-articular components. With the kneeresting in this position, anteroposteriorstereopair macroradiographs (magnificationX 7 to X 9) of the medial and lateraltibiofemoral compartments were obtained atthe same angle as in the weight bearingmodified tunnel view. As already explained, itwas necessary to obtain the macroarthrogramsin the non-weight bearing position to avoid theappearance of a fluid level in the joint. Theremaining details were as already described forpreparation ofthe stereopair macroradiographsin the tunnel view of the joint.

METHODS OF ASSESSMENT

Qualitative assessment. The stereopairmacroradiographs obtained were examined, bya single observer, under a Large FormatStereoscope (Ross Instruments, Salisbury,UK), which permitted a three dimensionalevaluation of the joint structure.5 6 Articularcartilage damage was graded as none (smoothcartilaginous surface with no apparentthinning), mild (minimal thinning andirregularity), moderate (large localised defectsand moderate thinning and irregularity), orsevere (severe denudation of cartilage). Itsextent was judged by assessing whether it wasconfined to only the outer, middle or innerthirds of the femoral and tibial cartilages in themedial and lateral compartments. Additional

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JSWas a measure of cartilage thickness in knee OA

Medial

A

B0 M

Figure 2 Diagrams of the medial tibiofemoralcompartment ofan osteoarthritic knee illustrating the threesites at which macroradiographic measurements werecarried outfor determining the joint space width in thetunnel view of the knee joint (A) and thefemoral and tibialarticular cartilage thicknessfrom the double contrastmacroarthrogram (B). Measurements were taken across theouter (0), middle (M) and inner (I) one third of both themedial and lateral compartments at the joint.

observations included the extent of osteo-phytosis,4 subchondral sclerosis4 and meniscalcartilage damage. Using a four point scale, themeniscal cartilages were graded as notdamaged (normal contour without evidence ofswelling or tear), midly damaged (localisedmeniscal swelling or tear), moderatelydamaged (moderate size tear or degeneration),or severely damaged (extensive tear or

disintegration).Quantitative assessment. For this procedure,

the same observer examined the stereopairmacroradiographs under the stereoscope. Theright hand, back illuminated carriage com-

prised a digitiser tablet linked to an MOP-Videoplan (Zeiss, Hertfordshire, UK).'6A detailed description of the method of

measuring the x ray features and its accuracyin recording them is reported elsewhere;'6 itscoefficient of variation for linear JSWmeasurements is 37%/.16 The data, which were

Figure 3 Part of the double contrast macroarthrogram of the medial compartment ofanosteoarthritic knee taken at X 8 magnification, showing contrast medium imbibition in thetibial and meniscal cartilages changes that we havefound to be associated with cartilagefibrillation andfissuring. '5 The wire grids visible in this and the other macroarthrograms wereused to determine the radiographic magnification. Ho,izontal bar represents 36 mm.

initially recorded on microcomputer disks,were transferred to an IBM PC/AT computerand combined into a single large data file.Statistical analysis was carried out using theSPSS/PC+ package.'7

MEASUREMENTS

J7oint space width was measured using themacroradiographs of the weight bearing tunnelview of the knee. As shown in figure 2, JSW(defined as the interbone distance) wasmeasured (in millimetres) at three sites alongthe joint margin of both the medial and lateraltibiofemoral compartments. The sites wereobtained by subdividing the articulatingsurface of the joint into four and themeasurements were taken at the quarter, midand three-quarter divisions.

Articular cartilage thickness was measuredusing the double contrast macroarthrograms.It was represented by the distance between thearticular surface, identified by the presence ofa thin layer of contrast medium over and withinit (fig 3), and the mineralised osteochondraljunction. This distance was measured (inmillimetres) at the same sites over the femoralcondyles and tibial plateaux as those chosen forthe measurement of JSW in the plain filmmacroradiographs and shown in figure 2.

ANALYSIS OF THE DATA

Comparability of JSW and articular cartilagethickness measurements made at the individualsites in the two compartments was assessedusing the Wilcoxon matched pairs test.Comparison of each parameter between thereference and OA knees was assessed using theMann-Whitney test. The degree of correlationbetween JSW and articular cartilage thicknesswithin the medial and lateral knee compart-ments of the OA patients was assessed usingPearson's correlation coefficient (r) and thenon-parametric Kendall's Tc test methods.The latter test was used because of its greaterpower in determining the degree of associationbetween parameters which may not have astrict linearity of fit.'8 For all tests, p values lessthan 0 05 were considered statistically sig-nificant.

ResultsQualitative assessment of the plain filmsrevealed 11 knees were Kellgren and Lawrencegrade I, six were grade II, and three grade III;there were none at grade IV.

PLAIN FILM MACRORADIOGRAPHY IN THEWEIGHT BEARING TUNNEL VIEW

Osteophytes that were doubtful on con-ventional radiography were clearly visible onmacroradiography. The latter revealed thatosteophytes and subchondral sclerosis werepresent in the medial compartment of all 20OA knees. In the lateral compartmentosteophytes were present in seven andsubchondral sclerosis in 15.

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Table 1 Joint space width (JSW) measuredfrom weight bearing tunnel viewmacroradiographs ofhealthy kneesfrom the reference group of non-arthritic volunteers andpatients with knee OA, together with the sum offemoral and tibial cartilage thicknessesmeasuredfrom the double contrast macroarthrograms of the OA knees without weightbearing

Loaded JSW (mm) Sum offemoral and tibialcartilage thicknesses (mm)

Healthy knees OA knees OA knees(n = 14) (n = 20) (n = 20)

Medial compartmentOuter 4-45 (4-14 to 4-76) 3-21 (2-54 to 3-88)* 3-00 (2-35 to 3-65)Middle 4-55 (4-15 to 4-95) 3-35 (2-65 to 4-05)** 3-70 (2-96 to 4-44)Inner 5-77 (5-33 to 6-20) 4-56 (4-00 to 5-12)*** 4-75 (4-11 to 5-39)

Lateral compartmentOuter 5-46 (4-88 to 6-04) 4-74 (4-03 to 5-45) 4-50 (3-70 to 5-30)Middle 5-20 (4-68 to 5-72) 5-15 (4-51 to 5-79) 6-10 (5-60 to 6-60)Inner 5-66 (5-09 to 6-22) 5-04 (4-55 to 5-53) 4-61 (3-89 to 5-33)

Values are mean (95% confidence interval). Significant differences between healthy and OAknees: *p < 0-0008; **p < 0-01; ***p < 0-006 (Mann-Whitney test)

Jroint space width measurements. Comparedwith the reference range, the mean JSW in OAknees was significantly decreased in the medial,but not in the lateral compartment (table 1).It was decreased at all the three measurementsites: p < 0-0008 for the outer, p < 0-01 for themiddle, and p < 0-0006 for the inner site of thejoint margin (Mann-Whitney test) (table 1).

Figure 4 Part ofa double contrast macroarthrogram of the medial compartment ofanosteoarthritic knee taken at x 7 magnification, showing pronounced cartilage thinning overthe outer region of the tibial plateau and less severe thinning in the same region on thefemoral condyle. Horizontal bar represents 28 mm.

Figure 5 Part of the double contrast macroarthrogram of the medial compartment ofanosteoarthritic knee taken at x 6 magnification, showing cartilage thinning in the outer thirdof the tibial plateau andfemoral condyle. There is marked imbibition of contrast medium inboth articular cartilages, severalfocal lesions on thefemoral cartilage, and damage to themeniscus. Horizontal bar represents 18 mm.

Table 2 Double contrast macroradiographic findings of thenumber of osteoarthritic knees with meniscal and articularcartilage damage

Grade*

None Mild Moderate Severe

Articular cartilage damageMedial compartmentFemoral cartilage - 13 3 4Tibial cartilage - 10 4 6

Lateral compartmentFemoral cartilage - 16 3 1Tibial cartilage - 14 6

Meniscal damageMedial meniscus 6 5 4 5Lateral meniscus 9 7 3 1

*See text for explanation of grading scales.

DOUBLE CONTRAST MACROARTHROGRAPHY IN

THE NON-WEIGHT BEARING LATERAL POSITIONMeniscal and articular cartilage damage. Table

2 summarises the qualitative results of themeniscal and articular cartilage damage. Botharticular cartilage and menisci were moreseverely damaged in the medial than the lateralcompartments. In the medial compartment,damage to the meniscus was similar to that onthe surface of the tibial cartilage.

Imbibition of contrast medium, observed asa bright radiodense band on the surface ofarticular cartilage, was more extensive incartilage with moderate to severe (figs 4-6)compared with mild damage (fig 3). In jointswhere cartilage was grossly thinned and absent(fig 7), contrast medium had entered thesubchondral region.

Articular cartilage thickness measurements.Across the medial compartment of OA kneesthere was a gradient of articular cartilagethinning (table 1, figs 4-7): on average it wasthinnest at the outer site, intermediate at themiddle site, and thickest at the inner site onboth tibial and femoral surfaces (table 1). Thedifferences between sites were more pro-nounced on the tibial than the femoralsurfaces. By contrast, in the lateral compart-ment (table 1) the cartilage was on averagethickest at the middle site on both the jointsurfaces.

COMPARISON OF JSW AND CARTILAGETHICKNESS MEASUREMENTS IN OA KNEESThe degree of correlation between the twomeasurements differed in the two compart-ments. They were strongly correlated at allthree sites in the medial compartment (fig 8A),but only at the middle site in the lateral com-partment, where the correlation was weaker(fig 8B). The Pearson r values for the three sitesin the medial compartment were greater than0-911, with a Tc greater than 0-607(p <0000 1); that for the middle site in thelateral compartment was 0-657, with Tc 0 305(p <003).Comparison of the two parameters at indi-

vidual sites within the two compartmentsshowed the JSW to be significantly smallerthan the sum of the femoral and tibial cartilagethicknesses over the middle, but not over either

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Figure 6 Part of a double con

osteoarthritic knee taken at x 7outer third and pronounced thirOn the femoral condyle the surfclearly over the outer region. TIare present at the condyle and t,

L&.

Figure 7 Part ofa double con

osteoarthritic knee taken at X 7the outer and middle regions ofis visible at the inner region of t(arrowed). Thefemoral condyl,Breaks in thefemoral cortex ar

The meniscus has been severely

of the other sites (p < 0-001 and < 0 002 forthe medial and the lateral compartments,respectively).

DiscussionComparison of the JSW obtained from weightbearing tunnel view macroradiographs of OAknees with the sum of the tibial and femoralcartilage thicknesses measured from macro-

A arthrograms of the same knees in the non-weight bearing lateral position revealed ahighly significant correlation between the twomeasurements in the medial but not the lateralcompartment. Thus JSW reliably measures

trast macroarthrogram of the medial compartment ofan cartilage thickness in the medial compartmentmagnification, showing total articular cartilage lossfrom the of OA knees.izning over the middle region of the tibial plateau (arrowed). The present study indicates that, in OA,face of the cartilage is irregular and shows thinning more cartilage thinning occurs in a gradient acrossefree edge of the meniscus is badly damaged. Osteophytes the joint surface: the thinning was most'ibial margins. Horizontal bar represents 30 mm. pronounced, in all patients, over the outer and

least over the inner regions of the joint surface.Thinning at the outer region was greater on thetibial plateau than on the femoral condyle-anobservation that is consistent with there beinga greater load per unit area at the concave tibialcompared with the convex femoral articularsurfaces,'9-21 and the with the occurrence ofmeniscal damage in virtually all the patients.Under these circumstances the menisci can nolonger be assumed to have shock absorbingfunctionS.22

In the lateral compartment of the knee,although there was a poor correlation between

_ 1 JSW and the sum of the cartilage thicknessesacross the compartment as a whole (fig 8B),this was not the case in the middle region.Comparison with the reference value forhealthy knees showed that there was little if anythinning. However, cartilage thinning waspresent in the outer and inner thirds, but only

trast macroarthrogram of the medial compartment of an in the group of patients who already had'5 magnification, showing exposed subchondral bone over advanced joint space narrowing in the medialthe femoral tibial surfaces. A remnant of articular cartilage compartment. The arthrogram confirmed that*he tibia and at the inferior margin of the femoral notch

cmate.*. .!e is overlayed by a soft tissue layer rich in contrast medium. in the knees studied cartilage damage wase present, permitting contrast to enter the subchondral bone. present over either the outer or the inner thirdsdamaged and truncated. Horizontal bar represents 32 mm. of the femoral and tibial surfaces, but not

8.0A

8.0-B

A B~~~~

EA

E *AA A

1~~~~~ ~~~~~~~~~~~~~~~~At- *IW%*v -AA

G 4 0 *4 * t 'z' 4.0-0A~~~~~~~~~~~~~~

*0~~~~~~~~~a 40 *A U-C ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~C)

O 0AU* 2-0- 2-0-* A

O-t 2-0 4-06:0 80 2:0 4-0 6.0 8-0Sum of cartilage thicknesses (mm) Sum of cartilage thicknesses (mm)

Figure 8 Comparison of the joint space width from plainfilm macroradiographs and the sum offemoral and tibialarticular cartilage thicknesses measuredfrom the double contrast macroradiographs at the chosen outer (0), middle (U) andinner (A) sites of the joint in (A) the medial and (B) the lateral tibiofemoral compartments.

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simultaneously over both the regions. Thissuggests that two distinct mechanisms maybring about cartilage destruction in thiscompartment. Such details are missing frompublications on double contrast arthrographyby Thomas et al,'3 Butt et al,23 and Staple,24presumably because of the lack of magnifi-cation when using conventional radiography.The present study further stresses the value

of weight bearing views when assessingcartilage changes in OA knees. In addition, itreveals a new finding: namely, that the JSW inthe middle region of both compartments issmaller than the sum of the cartilagethicknesses. The radioanatomical meaning ofthis finding becomes apparent when we takeinto account the fact that the films used tomeasure JSW were obtained in the weightbearing position, while those used to measurethe cartilage thicknesses were obtained in thenon-weight bearing position. In the weightbearing tunnel view, the femoral condyle maybe expected to exert the greatest load across themiddle region of the tibial plateau,'9 thereforethe articular cartilage over the middle region inboth the compartments can be expected to becompressed. Thus, depending upon the stageof OA disease in the compartment, and theextent to which the biophysical properties ofcartilage may have been altered, JSW willreliably reflect cartilage compression andthinning.

Utilising high definition x ray equipment wehave shown that standardised joint position,radiography and mensural procedures help tomeasure cartilage thickness accurately andreliably as JSW. Similar attention to detailwould potentially improve the accuracy andreliability of JSW measurements using con-ventional radiography.

This work was supported by a grant from Ciba GeigyPharmaceuticals, UK. The authors wish to express theirgratitude to Mrs Alison Robins for her assistance during theradiographic procedures, to Mrs Sheila Bishop for typing themanuscript and Mr Kevin Fitzpatrick and Miss Sarah Smith fortheir photographic assistance.

1 Altman R, Fries J F, Block D A, et al. Radiologic assessmentof progression in osteoarthritis. Arthritis Rheuwm 1987; 30:1214-25.

2 Fife RS, Brandt K D, BraunsteinE M, et al. Relationshipbetween arthroscopic evidence of cartilage damage and

radiographic evidence of joint space narrowing in earlyosteoarthritis of the knee. Arthritis Rheuni 1991; 34:377-82.

3 Brandt K D, Fife R S, Braunstein E M, Katz B.Radiographic grading of knee osteoarthritis: relation ofthe Kellgren and Lawrence grade to a grade based on jointspace narrowing, and correlation with arthroscopicevidence of articular cartilage degeneration. ArthrintisRheurn 1991; 34: 1381-6.

4 Buckland-Wright J C, Macfarlane D G, Jasani M K, LvnchJ A. Quantitative microfocal radiographic assessment ofosteoarthritis of the knee from weight bearing tunnel andsemi-flexed standing views. J Rheunmatol 1994; 21:1734-41.

5 Buckland-Wright J C. A new high-definition microfocalX-ray unit. Brj7Radiol 1989; 62: 201-8.

6 Buckland-Wright J C, Bradshaw C R. Clinical applicationsof high-definition microfocal radiography. Br 7 Radiol1989;62:209-17.

7 Jonsson K, Buckwalter K, Helvie M, Niklason L, Martel W.Precision of hyaline cartilage thickness measurements.Acta Radiol 1992; 33: 234-9.

8 Buckland-Wright J C. Quantitative radiographv ofosteoarthritis. Ann Rheu,ol Dis 1994; 53: 268-75.

9 Kellgren J H, Lawrence J S. Radiological assessment ofosteoarthrosis. Annii Rheunm Dis 1957; 16: 494-501.

10 Dacre J E, Scott D L, Da Silva J A P, Welsh G, HuskissonE C. Joint space in radiologically normal knees. Br- 7Rheumatol 1991; 30: 426-8.

11 Karvonen R I, Negendank W G, Teitge R A, Reed A H,Miller P R, Fernandez-Madrid F. Factors affectingarticular cartilage thickness in osteoarthritis and ageing.YRheumatol 1994; 21: 1310-8.

12 LynchJ A, Buckland-Wright J C, Macfarlane D G. Precisionof joint space width measurement in knee osteoarthritisfrom digital image analysis of high definition macro-radiographs. Osteoarthritis Cartilage 1993; 1: 209-18.

13 Thomas R H, Resnick D, Alazraki N P, Daniel D,Greenfield R. Compartmental evaluation of osteoarthritisof the knee. A comparative study of available diagnosticmodalities. Radiology 1975; 116: 585-94.

14 Sartoris D J, Resnick D. Plain film radiography: routine andspecialized techniques and projections. In: Resnick D,Niwayama G, eds. Diagnosis of bone and joint disorders, 2ndedn. Philadelphia: WB Saunders, 1988: 2-54.

15 Spring M W, Buckland-Wright J C. Contrast mediumimbibition in osteoarthritic cartilage. BrjRadiol 1990; 63:823-5.

16 Buckland-Wright J C, Carmichael I, Walker S R.Quantitative microfocal radiography accurately detectsjoint changes in rheumatoid arthritis. Ann Rheum Dis1986;45:463-7.

17 Norusis M J. SPSS/PC+ for the IBMPC/XT/AT. Chicago:SPSS Inc., 1986.

18 Campbell M J, Machin D. Medical statistics: acommiionsenseapproach. New York: John Wiley, 1990; 82-6.

19 Simkin P A, Gravey D 0, Fiechtner J J. Roman arches,human joints and disease. Arthnitis Rheumn 1980; 23:1308-11.

20 Unsworth A. Biomechanics of articulations. Br7 Rheioniiatol1989; 28: 446-50.

21 Bullough P G, Walker PS. The distribution of load throughthe knee joint and its possible significance to the observedpatterns of articular cartilage breakdown. Bull Hosp JointDisOrthopInstit 1977;37: 110-23.

22 Kelly M A, Fithian D C, Chem K Y, Mow V C. Structureand function of the meniscus: basic and clinicalimplications. In: Mow V C, Ratcliffe A, Woo S L Y, eds.Bioniechanics of diarthrodialjoints, Vol. 1. New York:Springer-Verlag, 1990: 90-211.

23 Butt W P, McIntyre J L. Double contrast arthrographv inthe knee. Radiology 1969; 92: 487-99.

24 Staple T W. Extrameniscal lesions demonstrated by doublecontrast arthrographv of the knee. Radiology, 1972; 102:311-9.

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