Table 1 Studies examining the effect of age and sex on the relationship between physical activity and risk for developing knee OA
Author (year) | Study design/participants | Measure(s) of OA | Measure(s) of physical activity | Results: effect of age/sex |
|---|---|---|---|---|
Studies investigating self-reported symptomatic OA | ||||
   Felson et al. (2007) [11] | 9-year cohort study/1,279 participants from the Framingham Offspring cohort | Self-reported, symptomatic | Self-reported; frequency, type, intensity | No association between OA risk and the following in middle-aged and elderly individuals: walking (≥6 miles/week; OR 0.78, 95% CI 0.49 to 1.24); working up a sweat (≥3 times/week; OR 1.23, 95% CI 0.72 to 2.10); and activity level compared with peers (more active; OR 0.94, 95% CI 0.60 to 1.47) |
| Â | Â | Â | Â | Sex analyses did not alter the results |
   Sutton et al. (2001) [20] | Retrospective case-control study/1,080 healthy participants | Self-reported, symptomatic | Self-reported; parameters not specified | Individuals who retrospectively reported being active in early life had no increased risk for knee OA compared with age-matched control individuals who reported a sedentary lifestyle (14 to 19 years: OR 1.2, 95% CI 0.8 to 1.9 [P = 0.39]; 20 to 24 years: OR 1.0, 95% CI 0.6 to 1.6 [P = 1.0]) |
| Â | Â | Â | Â | Individuals who reported being highly active in early life (age 20 to 24 years) had an increased risk for knee OA (OR 1.60, 95% CI 0.94 to 2.73 [P = 0.085]) |
Studies investigating self-reported physician diagnosed OA | ||||
   Hootman et al. (2003) [10] | 12.8-year cohort study/5,284 participants from the Cooper Clinic | Self-reported, physician diagnosed | Self-reported; joint stress physical activity score (intensity, frequency, duration and type) | Increasing levels of physical activity were not associated with an increased risk for hip/knee OA for both men (high level: OR 1.07, 95% CI 0.47 to 2.42) and women (high level: OR 1.31, 95% CI 0.92 to 1.87) |
   Rogers et al. (2002) [13] | 2-year nested case-control study/415 cases and 1,995 control individuals from the Cooper Clinic | Self-reported, physician diagnosed | Self-reported; joint stress (based on activity type) | Physical activity involving low or moderate/high joint stress was associated with reduced risk for hip/knee OA in women (low: OR 0.58, 95% CI 0.34 to 0.99; moderate/high: OR 0.24, 95% CI 0.11 to 0.52) |
| Â | Â | Â | Â | In contrast to low joint stress activity, moderate/high joint stress activity was associated with reduced risk for hip/knee OA in men (OR 0.62, 95% CI 0.43 to 0.89) |
   Cheng et al. (2000) [8] | 10-year prospective, cohort study/16,961 patients from the Cooper Clinic | Self-reported, physician diagnosed | Self-reported; activity type, duration | High-level physical activity (running ≥20 miles per week) was significantly associated with hip/knee OA among younger men (OR 2.4, 95% CI 1.5 to 3.9) but not older men (OR 1.2, 95% CI 0.6 to 2.3) |
| Â | Â | Â | Â | Nonsignificant findings were reported for younger women (HR 1.5, 95% CI 0.4 to 5.1) and older women (HR 1.4, 95% CI 0.4 to 4.6) |
Radiographic studies investigating structural OA | ||||
   Felson et al. (2007) [11] | 9-year cohort study/1,279 participants from the Framingham Offspring cohort | Radiographic, structural | Self-reported; frequency, type, intensity | No association between OA risk and the following in middle-aged and elderly individuals: walking (≥6 miles/week; OR 1.10, 95% CI 0.73 to 1.66); working up a sweat (≥3 times/week; OR 1.24, 95% CI 0.77 to 2.00); and activity level compared with peers (more active; OR 0.94, 95% CI 0.63 to 1.40) |
| Â | Â | Â | Â | Sex analyses did not alter the results |
   McAlindon et al. (1999) [14] | 8-year longitudinal cohort study/473 participants from the Framingham study cohort | Radiographic, structural | Self-reported: Framingham physical activity index; activity type, duration | The number of hours/day of heavy physical activity was associated with risk for knee OA (≥4 hours heavy activity/day compared with no heavy activity; OR 7.0, 95% CI 2.4 to 20 [P = 0.0002]) |
|  |  |  |  | Heavy physical activity (≥4 hours/day) was associated with increased risk for OA in elderly men (OR 7.0, 95% CI 1.7 to 29) and women (OR 9.0, 95% CI 1.7 to 48) |
Radiographic studies investigating structural OA | ||||
   Felson et al. (1997) [17] | 8-year longitudinal study/598 participants from the Framingham Study cohort | Radiographic, structural | Framingham physical activity index; activity type | Habitual physical activity increased the risk for knee OA for participants in the highest quartile of physical activity compared with those in the lowest quartile (OR 3.3, 95% CI 1.4 to 7.5) |
| Â | Â | Â | Â | A sex-specific effect was observed in an elderly cohort (men: OR 3.8, 95% CI 0.9 to 17.3; women: OR 3.1, 95% CI 1.1 to 8.6) |
   Hannan et al. (1993) [18] | Longitudinal cohort study (conducted over 19 years)/1,415 individuals from the Framingham study cohort | Radiographic, structural, | Self-reported: duration, frequency, type; physical capacity measures: FEV, pulse rate | Habitual physical activity did not increase the risk for knee OA in elderly men or women (highest quartile; men: OR 1.34, 95% CI 0.66 to 2.74; women: OR 1.09, 95% CI 0.63 to 1.90) |
| Â | Â | Â | Â | In contrast to women, men in the highest quartile of habitual physical activity had significantly elevated rates of asymptomatic osteophytes (OR 2.14, 95% CI 1.01 to 4.54) |
   White et al. (1993) [12] | Case-control study/305 physical education teachers and age-matched control individuals | Radiographic, structural | Self-reported; frequency, duration | There was a significantly lower prevalence of knee OA in middle-aged physical education teachers compared with the control individuals in both 'younger' (48 to 54 years [P < 0.001]) and 'older' (55 to 60 years [P < 0.001]) age categories |