The value of exercise for people with knee osteoarthritis (OA) receives continuing consideration. The optimal length of study follow-up time remains unclear. A group of individuals with knee OA participating in an exercise intervention was followed for 2 years. The authors quantified the change in knee-pain scores during Months 1-12 and during Months 13-24. Eleven individuals with radiographic knee OA and knee-pain scores of 2+ were evaluated. Pain scores were collected weekly from participants who exercised three times a week. Participants demonstrated pain reduction during both time periods. Pain reduction during Months 13-24, -10.7%, was slightly higher than pain reduction during Months 1-12, -7.8%. Among people with knee OA who exercise, these findings suggest that knee-pain amelioration continues beyond 12 months. Clinicians should consider encouraging long-term exercise programs for knee-OA patients. To best characterize the effect of exercise on knee pain, researchers designing clinical trials might want to lengthen the studies' duration.