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)

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])

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)

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)

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)

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)

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)

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

CI, confidence interval; FEV, forced expiratory volume; HR, hazard ratio; OA, osteoarthritis; OR, odds ratio.

Urquhart et al. Arthritis Research & Therapy 2008 10:203   doi:10.1186/ar2343