Figure 1.

Flow diagram of selection and classification of participants enrolled in the Osteoarthritis Initiative study

^¶OAI, online database provided by coordinating center, University of California, San Francisco (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.

^§No pain in both knees with no back pain.

^€No pain in both knees with back pain.

^‡Pain in both knees without back pain.

^ᴥPain in both knees and back pain.