Table 2

Studies examining the effect of BMI 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 BMI

Studies investigating self-reported symptomatic OA

Felson et al. (2007) [11]

9-year longitudinal cohort study/1,279 participants from the Framingham Offspring cohort

Self-reported, symptomatic

Self-reported; frequency, type, intensity

Overall results are presented in Table 1

Among persons with BMI above the median, there was no relationship between the risk for knee OA and the following: walking (≥6 miles/week; OR 0.84, 95% CI 0.37 to 1.92); working up a sweat (≥3 times/week; OR 1.04, 95% CI 0.55 to 1.96); and activity level compared with peers (more active; OR 0.63, 95% CI 0.35 to 1.16)

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 the joint stress physical activity score 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)

BMI did not modify the relationship between moderate physical activity and risk for knee OA for both men (OR 1.07, 95% CI 1.03 to 1.11) and women (OR 1.12, 95% CI 1.06 to 1.19)

Radiographic studies investigating structural OA

Felson et al. (2007) [11]

9-year longitudinal cohort study/1,279 participants from the Framingham Offspring cohort

Radiographic, structural

Self-reported; frequency, type, intensity

Overall results presented in Table 1

Among persons with BMI above the median, there was no relationship between the risk of radiographic knee OA and the following: walking (≥6 miles/week; OR 0.95, 95% CI 0.55 to 1.62); working up a sweat (≥3 times/week; OR 1.22, 95% CI 0.67 to 2.21); and activity level compared with peers (more active; OR 0.82, 95% CI 0.48 to 1.40)

McAlindon et al. (1999) [14]

8-year longitudinal cohort study/473 participants from the Framingham Heart Study cohort

Radiographic, structural

Self-reported: Framingham physical activity index; activity type, duration

The number of hours per 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])

Risk for OA was greatest among individuals in the upper tertile of BMI (≥3 hours/day of heavy physical activity; OR 13.0, 95% CI 3.3 to 51)

Kujala et al. (1995) [15]

Retrospective cohort study/117 male former top-level athletes

Radiographic, structural

Self-reported; parameters not-specified

Risk for knee OA was increased in athletes with a higher BMI at age 20 years (OR 1.76/unit increase, 95% CI 1.26 to 2.45)

BMI, body mass index; CI, confidence interval; OA, osteoarthritis; OR, odds ratio.

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