Sociodemographic and Clinical Correlates of Physical Therapy Utilization in Adults With Symptomatic Knee Osteoarthritis

Background. Physical therapy is essential for conservative management of symptomatic knee osteoarthritis (OA). However, physical therapy utilization data are limited for knee OA. Objective. The purpose of this study is to identify correlates of physical therapy utilization among adults with symptomatic knee OA. Design. The design consisted of secondary analysis using baseline data from a randomized controlled trial of 350 adults with physician-diagnosed symptomatic knee OA. Methods. Patients completed baseline surveys regarding demographics, pain, function, medical history, and prior physical therapy utilization for symptomatic knee OA. Multivariable logistic regression identified correlates of physical therapy utilization, with models adjusted for body mass index and age. Interactions of race and sex with all other characteristics were evaluated. Results. One hundred and eighty-one patients (52%) reported prior physical therapy utilization. Factors independently associated with increased odds of physical therapy utilization were female sex (odds ratio [OR] =3.06, 95% CI = 1.58-5.93), bachelor degree or higher degree (OR = 2.44, 95% CI = 1.15-5.16), prior knee injury (OR = 1.86, 95% CI = 1.08-3.19), and duration of knee OA symptoms (OR = 2.16, 95% CI = 1.09-4.29 for >5-10 years; OR = 2.11, 95% CI = 1.10-4.04 for >10 years). Whites who had received a joint injection were >3 times as likely to have utilized physical therapy (OR = 3.69, 95% CI = 1.94-7.01); this relationship did not exist for non-whites who had received joint injections. Limitations. A sample enrolled in an exercise study may limit generalizability. Self-report of physical therapy may misclassify utilization. It cannot be determined whether lack of utilization resulted from lack of referral or from patients choosing not to attend physical therapy. Conclusion. Physical therapy is underutilized to manage symptomatic knee OA. Women and those with a bachelor degree or higher degree, prior knee injury, and longer duration of knee OA symptoms were more likely to have used therapy previously. Differences by race in the link between joint injection and physical therapy utilization may reflect a reduced likelihood of referral and decreased use of health interventions for symptomatic knee OA among non-whites, or both.