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Tables
Baseline Characteristics Study Population for Incident Frequent Knee Pain§§ (n = 237) Study Population for Incident Symptomatic Knee OA¶¶ (n = 235) Questionnaire variables Age (years), mean (SD) 55.7 ± 3.2 55.8 ± 3.2 BMI (kg/m2), mean (SD) 31.9 ± 3.8 31.9 ± 3.8 Postmenopausal status, n (%) 159 (67) 159 (68) Comorbidity of depression*, n (%) 16 (7) 16 (7) Family history of OA†, n (%) 113 (48) 112 (48) History of knee injury‡, n (%) 46 (19) 47 (20) Physically demanding work§, n (%) 24 (10) 24 (10) Mild knee symptoms¶, n (%) 98 (41) 100 (43) Feeling of giving way‖, n (%) 35 (15) 37 (16) Knee problems while climbing stairs**, n (%) 20 (8) 20 (9) Knee problems standing up from chair**, n (%) 56 (24) 58 (25) Morning stiffness††, n (%) 29 (12) 29 (12) Swollen knee‡‡, n (%) 27 (11) 27 (11) Physical examination variables Heberden's nodes (in ≥1 finger), n (%) 65 (27) 64 (27) Joint line tenderness (medial and/or lateral), n (%) 26 (11) 25 (11) Crepitus during active motion, n (%) 134 (57) 135 (57) BMI, body mass index; N, number of women; OA, Osteoarthritis; SD, standard deviation.
↵* Comorbidity of depression was defined as being diagnosed with depression and/or currently under treatment.
↵† Present when at least one first-degree relative had OA.
↵‡ Present when visited a doctor for a knee injury.
↵§ Doing heavy physical work “quite often” or “(almost) always”.
↵¶ Pain in or around the knee within the last 12 months.
↵‖ The sensation of the knee giving way within the last 12 months.
↵** Defined with the Knee Injury and Osteoarthritis Outcome Score (KOOS) on physical functioning.
↵†† Defined with the KOOS on stiffness.
↵‡‡ Defined with the KOOS on symptoms.
↵§§ Incident frequent knee pain after 2.5 and/or 6.5 years was defined when frequent knee pain was present at 2.5 and/or 6.5 years and when no knee pain was reported at baseline. Frequent knee pain was defined as self-reported pain in or around one or both knees during most days in the past month.
↵¶¶ Incident symptomatic knee OA after 2.5 and/or 6.5 years was defined when incident symptomatic knee OA was present at 2.5 and/or 6.5 years and not present at baseline. Symptomatic knee OA was defined according to the clinical and radiographic ACR criteria: self-reported frequent knee pain and a definite osteophyte in the tibiofemoral joint of the same knee and one of the following: age >50 years, morning stiffness <30 minutes, crepitus on active motion of the knee.
- Table 2.
Multivariable Models in Prediction of Incident Frequent Knee Pain and Internal Validation (Calibration and Discrimination) of the Risk Prediction Models
Selected Predictors Basic Model Backward Model OR (95% CI) P Value OR (95% CI) P Value Age (years) 1.07 (0.98–1.16) .16 1.15 (1.03–1.28) .02 BMI (kg/m2) 1.09 (1.01–1.17) .02 1.13 (1.04–1.23) .004 Mild knee symptoms* 1.74 (0.88–3.44) .12 Knee problems while climbing stairs† 2.06 (1.03–4.12) .04 Morning stiffness‡ 3.03 (1.17–7.81) .02 Postmenopausal status 0.57 (0.28–1.18) .13 Physically demanding work§ 2.05 (0.72–5.83) .18 AUC of the model 0.63 (0.55–0.71) 0.71 (0.63–0.78) Calibration: Hosmer-Lemeshow P value .72 .93 Variance explained (Nagelkerke), % 4.6 21.0 AUC, area under the curve of the receiver operating characteristic; BMI, body mass index; CI, confidential interval; OR, odds ratio.
Bold indicates P < .05.
↵* Pain in or around the knee within the last 12 months.
↵† Defined with the Knee Injury and Osteoarthritis Outcome Score (KOOS) on physical functioning.
↵‡ Defined with the KOOS on stiffness.
↵§ Doing heavy physical work “quite often” or “(almost) always”.
- Table 3.
External Validation for the Prediction of Incident Frequent Knee Pain in Rotterdam Study-III-1
Candidate Predictor Study Population (n = 236) OR (95% CI) P Value Age (years) 1.01 (0.89–1.15) .88 BMI (kg/m2) 1.08 (0.98–1.18) .13 Mild knee symptoms* 1.80 (0.84–3.87) .13 Knee problems while climbing stairs† 2.14 (0.95–4.82) .07 Morning stiffness‡ 1.65 (0.66–4.16) .29 Postmenopausal status 0.98 (0.36–2.69) .96 Physically demanding work§ 1.14 (0.49–2.66) .76 AUC of the model 0.71 (0.62–0.79) Calibration: Hosmer-Lemeshow P value .57 Variance explained (Nagelkerke), % 12.2 AUC, area under the curve of the receiver operating characteristic; BMI, body mass index; CI, confidential interval; OR, odds ratio.
↵* Pain in or around the knee within the last 12 months.
↵† Defined with the Knee Injury and Osteoarthritis Outcome Score (KOOS) on physical functioning.
↵‡ Defined with the KOOS on stiffness.
↵§ Defined as doing intense work (regularly lifting heavy objects at work).
- Appendix Table 1.
Multivariable Models in Prediction of Incident Symptomatic Knee Osteoarthritis (OA) and Internal Validation (Calibration and Discrimination) of the Risk Prediction Models
Selected Predictors Basic Model Backward Model OR (95% CI) P Value OR (95% CI) P Value Age (years) 1.07 (0.98–1.17) .15 1.14 (1.02–1.28) .02 BMI (kg/m2) 1.12 (1.04–1.20) <.01 1.16 (1.06–1.26) .001 Mild knee symptoms* 1.73 (0.85–3.49) .13 Knee problems while climbing stairs† 2.08 (1.03–4.23) .04 Morning stiffness‡ 2.46 (0.97–6.25) .06 Postmenopausal status 0.54 (0.26–1.12) .10 Physically demanding work§ 2.38 (0.83–6.83) .11 AUC of the model 0.63 (0.54–0.71) 0.72 (0.64–0.80) Calibration: Hosmer-Lemeshow P value .96 .20 Variance explained (Nagelkerke), % 6.5 21.9 AUC, area under the curve of the receiver operating characteristic; BMI, body mass index; CI, confidential interval; OR, odds ratio.
Bold indicates P < .05.
↵* Pain in or around the knee within the last 12 months.
↵† Defined with the Knee Injury and Osteoarthritis Outcome Score (KOOS) on physical functioning.
↵‡ Defined with the KOOS on stiffness.
↵§ Defined as doing intense work (regularly lifting heavy objects at work).
- Appendix Table 2.
External validation for the prediction of incident symptomatic knee Osteoarthritis (OA) in Rotterdam Study-III-1
Selected Predictors Study Population (n = 264) OR (95% CI) P Value Age (years) 1.13 (0.93–1.37) .22 BMI (kg/m2) 1.09 (0.97–1.22) .15 Mild knee symptoms* 1.53 (0.49–5.08) .44 Knee problems while climbing stairs† 4.47 (1.31–15.23) .02 Morning stiffness‡ 2.14 (0.68–6.73) .19 Postmenopausal status 1.33 (0.22–7.98) .76 Physically demanding work§ 1.50 (0.50–4.53) .48 AUC of the model 0.81 (0.71–0.90) Calibration: Hosmer-Lemeshow P value .17 Variance explained (Nagelkerke), % 21.9 AUC, area under the curve of the receiver operating characteristic; BMI, body mass index; CI, confidential interval; OR, odds ratio.
Bold indicates P < .05.
↵* Pain in or around the knee within the last 12 months.
↵† Defined with the Knee Injury and Osteoarthritis Outcome Score (KOOS) on physical functioning.
↵‡ Defined with the KOOS on stiffness.
↵§ Defined as doing intense work (regularly lifting heavy objects at work).
