Table 5.

Prevalence of Frequent Knee Pain, Radiographic OA, and Symptomatic Knee OA based on the counts of swimming participated in within the earlier age periods (12 – 18 and 19 – 34). Results are presented unadjusted and adjusted with 95%CIs.

Frequent Knee Pain	Unadjusted Prevalence (95% CI)	Adjusted* Prevalence (95% CI)
Number of time periods of swimming
0 (n = 1730)	40.1% (38.7 – 43.2%)	40.0% (37.6 – 42.4%)
1 (n = 536)	38.0% (35.7 – 40.3%)	35.7% (33.3 – 38.2%)
2 (n = 356)	35.0% (30.9 – 39.4%)	35.7% (31.3 – 40.3%)
	p for trend=0.03	p for trend=0.6
Radiographic OA
Number of time periods of swimming
0 (n = 1730)	60.0% (57.8 – 62.3%)	60.0% (58.5 – 63.4%)
1 (n = 536)	55.6% (53.2 – 57.9%)	53.9% (51.3 – 56.5%)
2 (n = 356)	51.0% (46.5 – 55.5%)	52.2% (47.3 – 57.1%)
	p for trend=0.0008	p for trend=0.03
SOA
Number of time periods of swimming
0 (n = 1730)	29.1% (27.1 – 31.2%)	26.9% (24.7 – 29.1%)
1 (n = 536)	25.5% (23.5 – 27.8%)	22.0% (19.9 – 24.2%)
2 (n = 356)	22.2% (18.8 – 26.1%)	21.3% (17.8 – 25.3%)
	p for trend=0.005	p for trend=0.2

^*Adjusted for age, sex, BMI, BMI at age 25, history of knee injury, and all other leisure activities correlated with swimming during the respective age ranges.