FIGURE 1.

Flow diagram of selection and classification of subjects enrolled in the Osteoarthritis Initiative study that was included in the present study.

^*The Osteoarthritis Initiative Study has made large, heterogeneous data sets available for public use (http://oai.epi-ucsf.org/datarelease/).

^†Subjects with symptomatic tibiofemoral knee osteoarthritis at baseline.

^‡Subjects with no symptomatic tibiofemoral osteoarthritis in either knee at baseline.

^§Subjects with no pain, aching, or stiffness in either knee in the past year; no radiographic finding of osteoarthritis; and no eligibility risk factors.

^lInfrequent pain in one knee and no pain in the other knee or infrequent pain in both knees.

^¶Data missing for the variable indicating which knee was eligible for the study.

^#Frequent pain in both knees.

^**Frequent pain in one knee, no pain in the other knee.

^††No pain in either knee.