Pain related to knee osteoarthritis (OA) is a complex phenomenon that cannot be fully explained by radiographic disease severity. We hypothesized that pain phenotypes are likely to be derived from a confluence of factors across multiple domains: knee OA pathology, psychology, and neurophysiological pain processing. The purpose of this study was to identify distinct phenotypes of knee OA, using measures from the proposed domains. Data from 3494 subjects participating in the Osteoarthritis Initiative (OAI) study was analyzed. Variables analyzed included: radiographic OA severity (Kellgren-Lawrence grade), isometric quadriceps strength, Body Mass Index (BMI), comorbidities, CES-D Depression subscale score, Coping Strategies Questionnaire Catastrophizing subscale score, number of pain sites, and knee tenderness on physical examination. Variables used for comparison across classes included pain severity, WOMAC disability score, sex and age. Latent Class Analysis was performed. Model solutions were evaluated using the Bayesian Information Criterion. One-way ANOVAs and post hoc least significance difference tests were used for comparison of classes.Introduction
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Early postoperative strength loss is pronounced following total knee arthroplasty (TKA) and is largely the result of reduced muscular activation. High-intensity progressive rehabilitation may limit postoperative weakness and improve long-term outcomes, but no randomized controlled trials have examined its use after TKA. The purpose of this trial was to examine the efficacy of a high-intensity progressive rehabilitation protocol (HI) compared to a lower intensity (LI) rehabilitation protocol after TKA. One hundred and sixty-two subjects (aged 63±7 years, 89 females) were randomized to either the HI group or LI groups after TKA. The HI intervention consisted of an early initiation of intensive rehabilitation using progressive resistance exercise. The LI intervention was based on a synthesis of previously published standard TKA rehabilitation programs. Both groups were treated 2–3 times per week for 12 weeks. Outcomes included the stair climbing test, timed-up-and-go test, five-times sit-to-stand test, 6-minute walk test, isometric quadriceps and hamstring strength, quadriceps activation, surgical knee range of motion, and WOMAC. Secondary analysis evaluated whether outcomes differed depending on post-operative quadriceps activation. Outcomes were assessed preoperatively and at 1, 2, 3, 6, and 12 months postoperatively.INTRODUCTION
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