Table 3. Post Hoc Analysis of the Relative Risk of Achieving a Clinically Meaningful Change in WOMAC Pain Score.

Follow-up time	No./total (%) with significant pain reduction of ≥2 pointsa		Absolute risk difference, % (95% CI)	Risk ratio (95% CI)b	P valuec
	Diet and exercise	Attention control
6 mo	181/343 (52.8)	145/324 (44.8)	8 (0.45-15.6)	1.17 (1.00-1.35)	.045
18 mo	198/329 (60.2)	157/316 (49.7)	10.5 (2.9-18.1)	1.20 (1.04-1.38)	.01

Abbreviation: WOMAC, Western Ontario and McMaster Universities Osteoarthritic Index.

^a The minimum clinically important difference for pain is 1.6 (calculated as half the SD) on a 0- to 20-point scale.²⁴ This post hoc analysis is at the individual patient level, in which only whole numbers are possible. The 2-point criterion was recommended by the Osteoarthritis Research Society International as a moderate intervention response.³⁷

^b Relative risk of achieving a clinically meaningful change in pain, defined as a decrease in pain of 2 points or more on the Likert WOMAC pain scale (range, 0-20). Estimated by a generalized estimating equation model fit with contrasts for group comparisons at 6-and 18- month follow-up adjusted for baseline pain scores. The risk (ie, benefit) of achieving a significant decrease in pain increases from 6- to 18-month follow-up and is significantly greater in the diet and exercise group compared with the attention control group.

^c Test of the risk ratio under the null hypothesis that the risk ratio = 1.0.