Baseline Characteristics
| 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.