Table 1

Mean values and variability of clinical, radiographic, molecular and MRI-based risk factors in healthy reference knees and knees with radiographic osteoarthritis (ROA)

Healthy (n=75)ROA (n=77)
Risk factorMeanSDMeanSDPercentage differenceAUC (ROC)p Value (Wilcoxon)
Age (years)55.08.658.38.3
BMI (kg/m2)23.72.535.16.5
mJSW (mm)4.020.533.820.95
Anat. alignm. axis (°)182.42.10180.62.80−1.00.6890.0002
ln sIntactPINP3.720.513.660.47−1.80.5360.4489
ln sCTXI−1.390.69−1.450.67−4.10.5280.5370
ln uTINE_Cr3.380.843.200.67−5.40.5730.1439
ln pNPII0.870.930.630.92−27.20.5600.1614
ln sCPII5.970.435.880.35−1.60.6080.0165
ln sPIIANP6.480.666.600.701.90.5650.2186
ln uCTXII_Cr4.920.525.350.548.70.726<0.0001
ln sCOMP2.300.322.340.281.50.5310.4965
ln uARGS_Cr−0.630.78−0.800.80−26.10.5500.2382
ln uTIINE_Cr4.020.464.450.6210.60.715<0.0001
ln p15HETE5.530.515.630.601.90.5410.4566
ln pPGE23.501.053.870.8910.70.6130.0166
ln uOsteop_Cr1.711.231.381.21−19.10.5640.1674
ln sPIIINP1.120.341.290.3214.60.6610.0007
ln uTIIINE_Cr5.480.975.490.750.10.5190.7473
ln p3-NT7.010.447.270.453.70.6650.0006
Menisc_height (mm)−16.70.6200.0062
Menisc_sublux (mm)0.340.100.450.1731.40.695<0.0001
ThCtAB_MT (mm)1.580.181.660.194.70.6110.0223
ThCtAB_cMF (mm)1.690.221.700.300.40.5210.5679
  • The table reports bivariate analyses (ROA vs healthy knees) without adjustment for other factors.

  • AUC, area under the curve (from ROC analysis); p value, level of significance of differences between healthy and ROA knees determined using the Wilcoxon rank sum test (Fisher's exact test was used for ordinal variables, ie, OP and JSN scores). A p value given bold and in italics was significant at p<0.05 after correction for multiple testing using false discovery rates (FDR).

  • anat. alignment axis, anatomical knee axis determined from the Lyon Schuss (LS) radiographs (note there is an approximate 4° offset with the mechanical knee axis, ie, 184° is considered neutral alignment); BMI, body mass index; cMF, medial weightbearing femur; dGEMRIC, delayed gadolinium-enhanced MRI; MFTC, medial femorotibial compartment; menisc. height, meniscal height; menisc. Sublux, meniscal subluxation; Menisc_%Cover, percentage of tibial plateau covered by meniscus; mJSW, minimal joint space width measured quantitatively in LS radiographs; molecular markers (ln, natural logarithmic transformation) from urine (u), plasma (p), or serum (s): sIntactPINP, (intact) N-terminal propeptide of type I procollagen (μg/l); MT, medial tibia; OP, ordinal osteophyte scores (range 0–3) and JSN, ordinal joint space narrowing scores (range 0–3) obtained using LS radiographs and the Osteoarthritis Research Society International atlas in the MT and in the cMF; pNPII, N-terminal propeptide of type II procollagen (ng/ml), sCPII, C-terminal propeptide of type II procollagen (ng/ml); pPGE2, prostaglandin E2 (pg/ml); ROC, receiver operator characteristic; sCOMP, cartilage oligomeric matrix protein (U/l); sCTXI, C-terminal telopeptide of type I collagen (ng/ml); sPIIANP, N-terminal propeptide of type IIA procollagen (ng/ml); sPIIINP, N-terminal propeptide type III procollagen (ng/ml); ThCtAB, mean thickness (averaged over the total area of subchondral bone (tAB) in the MT and in the cMF); uARGS, aggrecan ARGS neoepitope (ng/mg creatinine): p15HETE, hydroxyeicosatetraenoic acid (pg/ml); uCTXII, C-terminal telopeptide of type II collagen (ng/mmol creatinine); uOsteop, osteopontin neoepitope peptide (ng/mg creatinine): p3-NT, plasma 3-nitrotyrosine (pg/ml); uTIIINE, type III collagen neoepitope (ng/mg creatinine); uTIINE, type II collagen neoepitope (ng/mmol creatinine); uTINE, type I collagen neoepitope peptides (ng/mg creatinine); WOMAC, Western Ontario and McMaster Universities scores: ranges are 0–20 for pain, 0–8 for stiffness and 0–68 for function (with higher values indicating more pain, more stiffness and worse function).