Background: Arthritis is the leading cause of disability among adults in the United States affecting twenty-one million adults. In addition, osteoarthritis is the second most costly chronic condition in the U.S. Physical activity is a challenge in all patients and is associated with fewer functional limitations and lower risk for developing illness. Currently, there are no objective measures of physical activity in advanced knee OA.
Objectives: The purpose of this study was to quantify patient-reported changes in pain and function during the natural progression of osteoarthritis at 3, 6, and 9 months, and to correlate these metrics with objective activity monitors.
Methods: 50 patients who were undergoing non-operative management of OA were enrolled. Patients were seen at baseline, 3 months, 6 months, and 9 months. At each visit, basic demographics and patient-reported measures (SF-36, WOMAC, and Charlson Co-morbidity index) were recorded. In addition, patients wore ActiGraph and activPal activity monitors for 7 days following the visit.
Results: The average age of the enrolled participants was 57 with 82% of participants being less than 65 years of age. Most participants were female (64%), and 80% of participants had 1 or fewer medical co-morbidities on the Charlson Co-morbidity Index. Only 4% of patients were using assistive devices. The average WOMAC pain score was 68 and did not change from one time period to the next. The average SF-36 PCS score was 38 and the MCS was 54, and neither changed over time. The average SF-36 PCS score in patients with a WOMAC pain score less than 80 was 36, while in those with a WOMAC pain score greater than 80 it was 42.5. In contrast, analyses of the activPal found a decline in activity over the time period. In the first 19 patients wearing the activPal who were analyzed, 12 of 19 increased sedentary time at 9 months by an average of 18%. In addition, 15 of 19 participants decreased minutes of moderate to vigorous physical activity (MVPA) at 9 months by an average of 26%.
Conclusions: In our study of 50 participants with osteoarthritis, patient-reported function did not change over a 9-month period. However, preliminary activity data suggests a decline. Further work will correlate patient-reported measures to the objective measures recorded by activity monitors to determine if objective monitors are preferable to detect early changes in activity due to OA.
 (CDC), Centers for Disease Control and Prevention. Prevalence of arthritis—United States, 1997. MMWR Morb Mortal Wkly Rep 2001. May 4; 50:334-6.
 Druss BG, Marcus SC, Olfson M, Pincus HA. The most expensive medical conditions in America. Health Affairs. 2002; 21:105-11.
 Centers for Disease Control and Prevention (CDC). Physical activity among adults with a disability—United States, 2005. MMWR Morb Mortal Wkly Rep 2007. Oct 5;56(39):1021-4.
- Physical activity,
Available at: http://works.bepress.com/franklinp/50/