Table 1.

Characteristics of the Study Sample.^*

Characteristic	Subjects (N = 991)
Age — yr	62.3±8.6
Female sex — no. (%)	565 (57)
White race — no. (%)†	922 (93)
Body-mass index‡	28.5±5.6
Current smoker — no./total no. (%)	106/946 (11)
Characteristics of the right knee — no./total no. (%)
Any pain, aching, or stiffness in the previous month	278/965 (29)
Pain, aching, or stiffness on most days	226/966 (23)
Any episode of buckling in the previous 3 months	64/964 (7)
Radiographic evidence of osteoarthritis§	171/963 (18)
Symptomatic osteoarthritis¶	90/942 (10)
Previous injury‖	139/966 (14)
Previous surgery	56/966 (6)

^*Plus–minus values are means ±SD.

^†Race was self-reported.

^‡The body-mass index is the weight in kilograms divided by the square of the height in meters. Data for the body-mass index were missing for 13 subjects.

^§Tibiofemoral osteoarthritis was defined as a grade of 2 or higher on the Kellgren–Lawrence scale.

^¶Symptomatic osteoarthritis was defined as knee pain, aching, or stiffness on most days and radiographic evidence of tibiofemoral osteoarthritis as defined by a grade of 2 or higher on the Kellgren–Lawrence scale.

^‖Previous injury was defined as a knee injury leading to a reduced ability to walk for at least 3 days or the use of crutches or a cane.