Differences between X-ray and MRI-determined knee cartilage thickness in weight-bearing and non-weight-bearing conditions

OBJECTIVE

Determine the effect of loading upon MRI-based mean medial femorotibial cartilage thickness (mMFT_th) and radiograph-based minimum joint space width (mJSW), and determine loading's effect on the relationship between these measures.

METHODS

MRI and radiographs were analyzed of 25 knees in weight-bearing and non-weight-bearing conditions. Eight subjects had a Kellgren-Lawrence (KL) grade of 0, indicating no evidence of radiographic OA. The rest were KL = 2 or KL = 3, indicating mild to moderate OA. The change from unloaded to loaded conditions was calculated.

RESULTS

Joint space measures decreased from unloaded to loaded conditions for both radiographs (mJSW = 3.29 mm unloaded to 3.16 mm loaded, P < 0.05) and MRI (mMFT_th = 2.70 mm unloaded to 2.55 mm loaded P < 0.001). The mean absolute difference measured from radiographs was larger for the OA group than the control group, at -0.20 mm for OA vs +0.01 mm for control. Loaded X-ray and loaded MRI joint space values from our study were no better correlated to one another than loaded X-ray and unloaded MRI.

CONCLUSION

Knee loading does not add a very significant value to the study of joint space on healthy knees, but loading may play a role in the study of OA knees. Unloaded MRI assessments of cartilage thickness are as correlated to loaded JSW as to loaded MRI measurements. More study is necessary to determine whether loaded MRI adds significant value to the study of OA progression.

Using ordered values of subregional cartilage thickness change increases sensitivity in detecting risk factors for osteoarthritis progression

OBJECTIVE

To examine whether ordered values of (sub)regional femorotibial cartilage thickness change are superior to region-based approaches in detecting risk factors for cartilage loss in osteoarthritis (OA).

METHODS

58 women with knee OA had 3 Tesla MR images acquired at baseline and 24 months. Changes in cartilage thickness (∆ThCtAB) were determined in eight medial femorotibial subregions. An ascending sort of individual ∆ThCtAB measurements was done to create "ordered values". Risk factors for cartilage loss considered were: age, BMI, anatomical knee axis (AAA), minimal (medial) joint space width (mJSW), and percent of medial tibial plateau covered by the meniscus (percent cover). All change metrics were tested for association with the risk factors using Kendall's τ and relative sensitivity of multiple tests of subregions and ordered values were compared with single metrics of change from plate and compartment summaries and the first ordered value.

RESULTS

The associations between subregion ∆ThCtAB and AAA (P=0.0002), mJSW (P=0.016), and age (P=0.011) were significant, but only AAA (at α=0.05) and age (at α=0.1) remained significant after adjusting for multiple subregions. In contrast, cMFTC had P-values<0.05 for AAA (P=0.0001), mJSW (P=0.016), and meniscus subluxation (0.04). The first ordered value had significant associations with AAA (P=0.0004), mJSW (P=0.003), meniscus subluxation (P=0.02) and percent cover (P=0.031) all of which were significant at α=0.05 after adjusting for tests on multiple risk factors.

CONCLUSION

Ordered values of ∆ThCtAB were more sensitive in detecting risk factors of cartilage loss than subregional ∆ThCtAB. Sensitivity was further enhanced by considering the minimum ordered value as a single test, thus not requiring adjustment for multiple tests. Using ordered values there was a significant association between ∆ThCtAB and baseline AAA, mJSW, meniscus subluxation and meniscus percent cover. This study provides an important step in validating ordered values of cartilage change.

The effects of acute loading on T1rho and T2 relaxation times of tibiofemoral articular cartilage

OBJECTIVE

To evaluate the effect of acute loading on healthy and osteoarthritic knee cartilage T(1ρ) and T(2) relaxation times.

DESIGN

Twenty subjects with radiographic evidence of osteoarthritis (OA) and 10 age-matched controls were enrolled. Magnetic resonance imaging (MRI) acquisition, including T(1ρ) and T(2) map sequences were performed unloaded and loaded at 50% body mass. Cartilage masks were segmented semi-automatically on registered high-resolution spoiled gradient-echo (SPGR) images for each compartment (medial and lateral). Cartilage lesions were identified using a modified Whole Organ Magnetic Resonance Imaging Score (WORMS) score. Statistical differences were explored using separate two-way (group×loading condition) Analysis of Variance (ANOVA) using age as a covariate to evaluate the effects of loading on T(1ρ) and T(2) relaxation times.

RESULTS

A significant decrease in T(1ρ) (44.5±3.8 vs 40.2±4.8ms for unloaded and loaded, respectively; P<0.001) and T(2) (31.8±3.8 vs 30.5±4.8ms for unloaded and loaded, respectively; P<0.001) relaxation times was observed in the medial compartment with loading while no differences were observed in the lateral compartment. This behavior occurred independent of WORMS score. Cartilage compartments with small focal lesions experienced greater T(1ρ) change scores with loading when compared to cartilage without lesions or cartilage with larger defects (P=0.05).

CONCLUSIONS

Acute loading resulted in a significant decrease in T(1ρ) and T(2) relaxation times of the medial compartment, with greater change scores observed in cartilage regions with small focal lesions. These data suggest that changes of T(1ρ) values with loading may be related to cartilage biomechanical properties (i.e., tissue elasticity) and may be a valuable tool for the scientist and clinician at identifying early cartilage disease.

Subregional femorotibial cartilage morphology in women--comparison between healthy controls and participants with different grades of radiographic knee osteoarthritis

OBJECTIVE

To identify subregional differences in femorotibial cartilage morphology between healthy controls and women with different grades of radiographic knee osteoarthritis (OA).

DESIGN

158 women aged > or =40 years were studied. Weight-bearing extended anterior-posterior (AP) and Lyon schuss radiographs were obtained and the Kellgren Lawrence grade (KLG) determined. 97 women had a body mass index (BMI)< or =28, no symptoms, and were AP KLG0. 61 women had a BMI> or =30, symptoms in the target knee, and mild (KLG2=31) to moderate (KLG3=30) medial femorotibial radiographic OA in the AP views. Coronal spoiled gradient echo water excitation sequences were acquired at 3.0 Tesla. Total plate and regional measures of cartilage morphology of the weight-bearing femorotibial joint were quantified.

RESULTS

KLG2 participants displayed, on average, thicker cartilage than healthy controls in the medial femorotibial compartment (particularly anterior subregion of the medial tibia (MT) and peripheral [external, internal] subregions of the medial femur), and in the lateral femur. KLG3 participants displayed significantly thinner cartilage than KLG0 participants in the medial weight-bearing femur (central subregion), in the external subregion of the MT, and in the internal subregion of the lateral tibia. These differences were generally unaffected when possible effects of demographic covariates were considered.

CONCLUSIONS

The results indicate that in femorotibial OA regional cartilage thickening and thinning may occur, dependent on the (radiographic) disease status of the joint. These changes appear to display a heterogeneous spatial pattern, where certain subregions are more strongly affected than others.

Change in regional cartilage morphology and joint space width in osteoarthritis participants versus healthy controls: a multicentre study using 3.0 Tesla MRI and Lyon–Schuss radiography

Objective:

Cartilage morphology displays sensitivity to change in osteoarthritis (OA) with quantitative MRI (qMRI). However, (sub)regional cartilage thickness change at 3.0 Tesla (T) has not been directly compared with radiographic progression of joint space narrowing in OA participants and non-arthritic controls.

Methods:

A total of 145 women were imaged at 7 clinical centres: 86 were non-obese and asymptomatic without radiographic OA and 55 were obese with symptomatic and radiographic OA (27 Kellgren–Lawrence grade (KLG)2 and 28 KLG3). Lyon–Schuss (LS) and fixed flexion (FF) radiographs were obtained at baseline, 12 and 24 months, and coronal spoiled gradient echo MRI sequences at 3.0 T at baseline, 6, 12 and 24 months. (Sub)regional, femorotibial cartilage thickness and minimum joint space width (mJSW) in the medial femorotibial compartment were measured and the standardised response means (SRMs) determined.

Results:

At 6 months, qMRI demonstrated a −3.7% “annualised” change in cartilage thickness (SRM −0.33) in the central medial femorotibial compartment (cMFTC) of KLG3 subjects, but no change in KLG2 subjects. The SRM for mJSW in 12-month LS/FF radiographs of KLG3 participants was −0.68/−0.13 and at 24 months was −0.62/−0.20. The SRM for cMFTC changes measured with qMRI was −0.32 (12 months; −2.0%) and −0.48 (24 months; −2.2%), respectively.

Conclusions:

qMRI and LS radiography detected significant change in KLG3 participants at high risk of progression, but not in KLG2 participants, and only small changes in controls. At 12 and 24 months, LS displayed greater, and FF less, sensitivity to change in KLG3 participants than qMRI.

Progressive increase in body mass index is not associated with a progressive increase in joint space narrowing in obese women with osteoarthritis of the knee

OBJECTIVE

Given that obesity is a risk factor for osteoarthritis (OA) of the knee, a study was undertaken to determine whether progressively higher body mass index (BMI) among obese women is associated with progressive increases in joint space narrowing (JSN).

METHODS

Medial compartment JSN over 12 months in Lyon Schuss radiographs of 60 obese women (BMI 30.0-50.5 kg/m(2)) with radiographic and symptomatic OA was compared with that in 81 non-obese women (BMI <28 kg/m(2)) with normal radiographs and minimal or no symptoms of knee OA.

RESULTS

Among the patients with OA, higher BMI tended to be associated with a higher Kellgren and Lawrence (KL) grade of OA severity. JSN in the non-obese controls was negligible, but in the 30 patients with KL grade 2 and KL grade 3 knees, mean (SD) JSN was 0.12 (0.31) mm and 0.32 (0.50) mm, respectively (p<0.005 and p<0.001). No association was seen between baseline BMI and 12-month JSN in patients with OA; indeed, the regression plot suggested a slight inverse relationship between the two.

CONCLUSIONS

In obese patients with OA, progressively higher BMI values were not accompanied by a progressively increasing rate of JSN. Joint loading was not evaluated, but it is possible that marked obesity limited the functional capacity of some subjects with OA, protecting their knees from loading. For investigators considering eligibility criteria for a trial of a structure-modifying OA drug, these data suggest that recruitment of patients with a BMI much higher than 30 kg/m(2) will not enrich the sample of subjects who will have more rapid JSN than those with a BMI of only 30 kg/m(2).

Performance of a non-fluoroscopically assisted substitute for the Lyon schuss knee radiograph: quality and reproducibility of positioning and sensitivity to joint space narrowing in osteoarthritic knees

OBJECTIVE

This study evaluated the longitudinal performance of a modified Lyon schuss (LS) knee examination in the detection of radiographic joint space narrowing (JSN) in knees with osteoarthritis (OA). The modified LS exam entails two to four iterative acquisitions with empirically adjusted angulation of the X-ray beam to achieve superimposition of the anterior and posterior margins of the medial tibial plateau (MTP), a marker of parallel radioanatomic alignment that the original LS exam achieves with fluoroscopically guided beam angulation.

METHODS

Seventy-four obese women with symptomatic knee OA underwent LS and fixed-flexion (FF, caudal 10 degrees beam angulation) X-ray exams at baseline and 1 year later. For 47 subjects, beam angulation for both LS exams was guided by fluoroscopy. For 27 subjects, the modified LS exam was performed at one or both times. Modified and original LS procedures were evaluated relative to concurrent FF radiographs with respect to the inter-margin distance (IMD) at the MTP midpoint (quality and reproducibility of alignment) and sensitivity to JSN.

RESULTS

Compared to FF radiographs, modified LS radiographs afforded a smaller mean IMD at baseline (0.89 vs 2.06 mm, P=0.002), more reproducible IMD (mean change=0.49 vs 0.91 mm, P=0.007) and more rapid JSN (mean=0.25 vs 0.02 mm/yr, P=0.005). These differences paralleled those observed between original LS and FF procedures with respect to baseline alignment (0.96 vs 1.94 mm, P<0.001), reproducibility of alignment (0.49 vs 1.00 mm, P<0.001) and sensitivity to JSN (0.16 vs -0.01 mm/yr, P=0.007).

CONCLUSION

In clinical centers where the absence of fluoroscopy equipment precludes use of the original LS protocol, a modified procedure employing iterative, empirical adjustment of the beam angle to achieve parallel radioanatomic alignment with the MTP affords a degree of superiority over the FF protocol with respect to quality and reproducibility of positioning and sensitivity to JSN in OA knees similar to that of the original.

One year change of knee cartilage morphology in the first release of participants from the Osteoarthritis Initiative progression subcohort: association with sex, body mass index, symptoms and radiographic osteoarthritis status

OBJECTIVE

The Osteoarthritis Initiative (OAI) is a multicentre study targeted at identifying biomarkers for evaluating the progression and risk factors of symptomatic knee OA. Here cartilage loss using 3 Tesla (3 T) MRI is analysed over 1 year in a subset of the OAI, together with its association with various risk factors.

METHODS

An age- and gender-stratified subsample of the OAI progression subcohort (79 women and 77 men, mean (SD) age 60.9 (9.9) years, body mass index (BMI) 30.3 (4.7)) with both frequent symptoms and radiographic OA in at least one knee was studied. Coronal FLASHwe (fast low angle shot with water excitation) MRIs of the right knee were acquired at 3 T. Seven readers segmented tibial and femoral cartilages blinded to order of acquisition. Segmentations were quality controlled by one expert.

RESULTS

The reduction in mean cartilage thickness (ThC) was greater (p = 0.004) in the medial than in the lateral compartment, greater (p = 0.001) in the medial femur (-1.9%) than in the medial tibia (-0.5%) and greater (p = 0.011) in the lateral tibia (-0.7%) than in the lateral femur (0.1%). Multifactorial analysis of variance did not reveal significant differences in the rate of change in ThC by sex, BMI, symptoms and radiographic knee OA status. Knees with Kellgren-Lawrence grade 2 or 3 and with a BMI >30 tended to display greater changes.

CONCLUSIONS

In this sample of the OAI progression subcohort, the greatest, but overall very modest, rate of cartilage loss was observed in the weight-bearing medial femoral condyle. Knees with radiographic OA in obese participants showed trends towards higher rates of change than those of other participants, but these trends did not reach statistical significance.

Change in cartilage morphometry: a sample of the progression cohort of the Osteoarthritis Initiative

OBJECTIVE

The performance characteristics of hyaline articular cartilage measurement on magnetic resonance imaging (MRI) need to be accurately delineated before widespread application of this technology. Our objective was to assess the rate of natural disease progression of cartilage morphometry measures from baseline to 1 year in knees with osteoarthritis (OA) from a subset of participants from the Osteoarthritis Initiative (OAI).

METHODS

Subjects included for this exploratory analysis are a subset of the approximately 4700 participants in the OAI Study. Bilateral radiographs and 3T MRI (Siemans Trio) of the knees and clinical data were obtained at baseline and annually in all participants. 160 subjects from the OAI Progression subcohort all of whom had both frequent symptoms and, in the same knee, radiographic OA based on a screening reading done at the OAI clinics were eligible for this exploratory analysis. One knee from each subject was selected for analysis. 150 participants were included. Using sagittal 3D DESSwe (double echo, steady-state sequence with water excitation) MR images from the baseline and 12 follow-up month visit, a segmentation algorithm was applied to the cartilage plates of the index knee to compute the cartilage volume, normalised cartilage volume (volume normalised to bone surface interface area), and percentage denuded area (total cartilage bone interface area denuded of cartilage).

RESULTS

Summary statistics of the changes (absolute and percentage) from baseline at 1 year and the standardised response mean (SRM), ie, mean change divided by the SD change were calculated. On average the subjects were 60.9 years of age and obese, with a mean body mass index of 30.3 kg/m2. The SRMs for cartilage volume of various locations are: central medial tibia -0.096; central medial femur -0.394; and patella -0.198. The SRMs for normalised cartilage volume of the various locations are central medial tibia -0.044, central medial femur -0.338 and patella -0.193. The majority of participants had a denuded area at baseline in the central medial femur (62%) and central medial tibia (60%). In general, the SRMs were small.

CONCLUSIONS

These descriptive results of cartilage morphometry and its change at the 1-year time point from the first substantive MRI data release from the OAI Progression subcohort indicate that the annualised rates of change are small with the central medial femur showing the greatest consistent change.

Precision of 3.0 Tesla quantitative magnetic resonance imaging of cartilage morphology in a multicentre clinical trial

OBJECTIVE

Quantitative MRI (qMRI) of cartilage morphology is a promising tool for disease-modifying osteoarthritis drug (DMOAD) development. Recent studies at single sites have indicated that measurements at 3.0 Tesla (T) are more reproducible (precise) than those at 1.5 T. Precision errors and stability in multicentre studies with imaging equipment from various vendors have, however, not yet been evaluated.

METHODS

A total of 158 female participants (97 Kellgren and Lawrence grade (KLG) 0, 31 KLG 2 and 30 KLG 3) were imaged at 7 clinical centres using Siemens Magnetom Trio and GE Signa Excite magnets. Double oblique coronal acquisitions were obtained at baseline and at 3 months, using water excitation spoiled gradient echo sequences (1.0x0.31x0.31 mm3 resolution). Segmentation of femorotibial cartilage morphology was performed using proprietary software (Chondrometrics GmbH, Ainring, Germany).

RESULTS

The precision error (root mean square coefficient of variation (RMS CV)%) for cartilage thickness/volume measurements ranged from 2.1%/2.4% (medial tibia) to 2.9%/3.3% (lateral weight-bearing femoral condyle) across all participants. No significant differences in precision errors were observed between KLGs, imaging sites, or scanner manufacturers/types. Mean differences between baseline and 3 months ranged from <0.1% (non-significant) in the medial to 0.94% (p<0.01) in the lateral femorotibial compartment, and were 0.33% (p<0.02) for the total femorotibial subchondral bone area.

CONCLUSIONS

qMRI performed at 3.0 T provides highly reproducible measurements of cartilage morphology in multicentre clinical trials with equipment from different vendors. The technology thus appears sufficiently robust to be recommended for large-scale multicentre trials.

Head-to-head comparison of the Lyon Schuss and fixed flexion radiographic techniques. Long-term reproducibility in normal knees and sensitivity to change in osteoarthritic knees

OBJECTIVE

The Lyon Schuss (LS) and fixed flexion (FF) views of the knee are superior to a conventional standing anteroposterior view in evaluating joint space narrowing (JSN) in osteoarthritis (OA). Both position the knee identically but only the LS aligns the medial tibial plateau (MTP) with the x-ray beam fluoroscopically. The present study provides the first head-to-head comparison of the LS and FF views.

METHODS

At baseline and 12 months, 62 OA and 99 control knees were imaged twice on the same day with LS and FF views. Minimum joint space width (mJSW) was measured by computer and MTP alignment was assessed from the distance between anterior and posterior margins of the MTP (intermargin distance, IMD). Reproducibility of measurements of mJSW and sensitivity to change were evaluated.

RESULTS

In normal knees, JSW did not vary over 12 months with either view. In OA knees, 12-month mJSN was 0.22 (0.43) mm with the LS view and -0.01 (0.46) mm with the FF view (p = 0.0002 and p = 0.92, respectively). Mean IMD was only half as large in LS as in FF views (0.9 (0.5) mm vs 1.9 (1.2) mm, p<0.0001).

CONCLUSIONS

LS and FF radiographs offer similar reproducibility in JSW measurement. However, presumably due to its superiority in aligning the MTP, the LS view is much more sensitive to JSN in OA knees.

Effect of medial tibial plateau alignment on serial radiographs on the capacity to predict progression of knee osteoarthritis

OBJECTIVE

To evaluate the effect of medial tibial plateau (MTP) alignment of serial radiographs on the capacity to detect associations between baseline characteristics and progression of joint space narrowing (JSN) in knee osteoarthritis (OA).

METHODS

Standardised posteroanterior weight-bearing knee radiographs of 83 knee OA patients were obtained at baseline and after 24 months using the non-fluoroscopic fixed-flexion protocol. Minimum joint space width (JSW) of the medial tibiofemoral joint spaces was measured manually in paired radiographs. Progression of JSN was defined by a change in JSW larger than the smallest detectable difference (0.4mm). Satisfactory MTP alignment was present if the distance between the anterior and posterior margins of the MTP was < or = 1mm. Standardised questionnaires were used to record age, sex and body mass index. Medial tibiofemoral JSN and osteophyte severity at baseline were graded with the Osteoarthritis Research Society International (OARSI) atlas.

RESULTS

Progression of JSN was observed in 31 (28.4%) of 109 OA knees. In the sub sample of 48 (44%) OA knees with satisfactory MTP alignment on baseline and 24-month radiographs, 18 (37.5%) knees progressed. Stronger (statistically significant) associations were found between sex, generalised OA, JSN and osteophyte severity at baseline and progression of JSN in the sub sample of radiographs with serial satisfactorily MTP alignment than in all radiographs together.

CONCLUSION

Insufficient quality of MTP alignment on serial radiographs could prevent detection of associations between baseline characteristics and progression of JSN in knee OA. These findings may have implications for longitudinal knee OA studies using the fixed-flexion protocol.

Fixed-flexion knee radiography: the sensitivity to detect knee joint space narrowing in osteoarthritis

OBJECTIVES

Independent reports on the longitudinal performance of non-fluoroscopic fixed-flexion knee radiography have not been published. Therefore, we evaluated the sensitivity of fixed-flexion radiography to detect knee joint space narrowing (JSN) over 2 years in patients with osteoarthritis (OA) and compared the effect of reproducibility and quality of medial tibial plateau (MTP) alignment on sensitivity to JSN.

METHODS

Fixed-flexion radiographs of both knees of 193 OA patients were obtained at baseline and after 24 months. Minimum joint space width (JSW) of the medial tibiofemoral joint spaces was measured manually in paired digitised radiographs without knowledge of the chronology. The degree of MTP alignment was assessed by measuring the distance between the anterior and posterior margins of the MTP (intermargin distance [IMD]). Accurate repositioning was achieved if, in the 24-month radiograph, the IMD was reproduced to within 1mm. The quality of MTP alignment was satisfactory if the IMD was <or=1mm.

RESULTS

The mean (standard deviation [SD]) JSN between baseline and 24 months was 0.18 (0.49)mm and the standardised response mean (SRM) was 0.37. The SRM was 0.36 in the knee film pairs (86%) in which the IMD was accurately reproduced after 24 months and 0.52 in the film pairs (42%) with satisfactory MTP alignment on both the baseline and 24-month radiographs.

CONCLUSION

The sensitivity to radiographic JSN on fixed-flexion knee radiographs over 2 years was higher in satisfactorily aligned than accurately reproduced serial pairs of radiographs. These findings have implications for longitudinal knee OA studies using fixed-flexion radiographs.

Association between concentrations of urinary type II collagen neoepitope (uTIINE) and joint space narrowing in patients with knee osteoarthritis

OBJECTIVE

To examine whether urine concentrations of type II collagen neoepitope (uTIINE) distinguish subjects with progressive radiographic and/or symptomatic knee osteoarthritis (OA) from those with stable disease.

METHODS

Subjects were 120 obese middle-aged women with unilateral knee OA who participated in a 30-month randomized-controlled trial of structure modification with doxycycline, in which a standardized semiflexed anteroposterior view of the knee was obtained at baseline, 16 months and 30 months. Subjects were selected from a larger sample to permit a priori comparisons between 60 OA progressors and 60 nonprogressors, as defined by joint space narrowing (JSN) in the medial tibiofemoral compartment. Each group contained 30 subjects who exhibited clinically significant increases in knee pain over 30 months and 30 who did not. Urine samples were obtained every 6 months for determination of the creatinine (Cr)-adjusted uTIINE concentration.

RESULTS

Baseline uTIINE levels were unrelated to JSN in the placebo group. However, among subjects in the active treatment group, a 1-standard deviation increment in baseline uTIINE (68 ng/mM Cr) was associated with a marginally significant, two-fold increase in the odds of progression of JSN (odds ratio 2.04, 95% confidence interval 0.98-4.28). The within-subject mean of uTIINE values at baseline, 6 months and 12 months was associated with concurrent JSN measured at 16 months (0.10mm of JSN per 69 ng/mM Cr, P=0.008). Similar results were seen in the interval between months 16 and 30 and in analyses using the maximum of intercurrent uTIINE levels.

CONCLUSION

Baseline uTIINE was not a consistent predictor of JSN in subjects with knee OA. However, serial measurements of uTIINE reflect concurrent JSN.

Urinary CTX-II levels are associated with radiographic subtypes of osteoarthritis in hip, knee, hand, and facet joints in subject with familial osteoarthritis at multiple sites: the GARP study

OBJECTIVE

To assess the relation between the urinary concentrations of type II collagen C-telopeptide (UCTX-II) and radiographic signs of osteoarthritis (ROA) in the GARP (Genetics, Arthrosis and Progression) study.

METHODS

UCTX-II levels were measured in GARP study participants, who are sibling pairs predominantly with symptomatic osteoarthritis at multiple sites. Kellgren and Lawrence scores were used to assess ROA in the knees, hips, hands, and vertebral facet joints, and spinal disc degeneration. A proportionate score was made for each joint location, based on the number of joints with ROA. The sum total ROA score represents a measure of cartilage abnormalities within each patient. By using linear mixed models the total ROA score and the joint site specific ROA scores were correlated with the UCTX-II level.

RESULTS

In 302 subjects the mean (SD) and median (range) for UCTX-II were 265 (168) and 219 (1346) ng/mmol creatine, respectively. There was a significant association between the total ROA score and UCTX-II levels. Subsequent multivariate analysis showed that the joint site specific ROA score at all joint sites, except for spinal disc degeneration, contributed independently to this association.

CONCLUSIONS

The total ROA score of GARP patients, representing cartilage abnormalities at the most prevalent ROA joint locations, showed an excellent correlation with UCTX-II levels. The specific ROA scores at the hip, hand, facet, and knee joints additively and independently explained this association. Even in patients with osteoarthritis at multiple sites, UCTX-II may be a sensitive quantitative marker of ROA.