Pain and Decreased Cognitive Function Negatively Impact Physical Functioning in Older Adults with Knee Osteoarthritis

ObjectiveWe hypothesized that among community-dwelling older adults without dementia with advanced chronic knee osteoarthritis (OA) pain: 1) higher levels of self-reported pain would be associated with decreased executive cognitive function and decreased physical function; and 2) decreased cognitive function would be associated with decreased physical function. MethodsSubstudy on 79 older adults who were participants in a Veterans Affairs clinical trial of periosteal stimulation therapy for advanced painful knee OA. Participants were 60 years, had radiographic evidence of Kellgren-Lawrence 3 or 4 knee OA on a standing anterior-posterior X-ray, had pain of at least moderate intensity and of at least 3 months' duration, and knee pain severity greater than pain severity in other parts of the body. Measures included computerized cognitive tests of executive function, pain, and physical function (gait speed and stair climbing). ResultsAs pain scores worsened, gait speed and stair climbing worsened (P=0.007 and P=0.035, respectively). Lower performance on the executive function tests was also significantly associated with decreased gait speed and stair climbing (P=0.002 and P=0.014, respectively). We did not find a significant relationship between pain and cognitive function. We explored the relationship between pain and physical function adjusted for executive functioning and found that pain was no longer associated with gait speed (P=0.06). ConclusionWorse pain scores and executive function scores were associated with worse physical function in older adults with painful knee OA. This suggests that slower gait speed in patients could be an indication to clinicians to monitor their patient's cognitive function. Executive function in particular affected the relationship between gait speed and pain, suggesting a possible mediating relationship.