Dynamic weight-bearing assessment of pain in knee osteoarthritis:construct validity, responsiveness, and interpretability in a research setting

BACKGROUND: The Osteoarthritis Research Society International (OARSI) has suggested to asses pain after specific activities consistently in clinical trials on knee OA. The Dynamic weight-bearing Assessment of Pain (DAP) assesses pain during activity (30 s of performing repeated deep knee-bends from a standing position). The purpose of this study is to evaluate the construct validity, responsiveness, and interpretability of the DAP for knee osteoarthritis (OA). METHODS: One-hundred participants with knee OA were tested twice each with the DAP, the Knee injury and Osteoarthritis Outcome Score (KOOS), six-minute-walk-test (6MWT), and 6-min-walk-test with subsequent pain rating (6MWTpain), and once with a transition questionnaire (TRANS-Q) for the patient-reported change in pain after 12 weeks of exercise. Construct validity (baseline-scores) and responsiveness (change-scores) were estimated by Spearman Correlation Coefficients. We hypothesized that no correlations would be excellent (<0.7) (divergent validity), except for the 6MWTpain (convergent validity). The TRANS-Q was used for interpreting the DAP change-scores in terms of responsiveness and Minimal Important Change (MIC). RESULTS: Divergent validity with the KOOS subscales (r = −0.31 to–0.45) and the 6MWT (r = −0.25) was supported. Convergent validity with the 6MWTpain was not supported (r = 0.54). The DAP change-scores corresponded to patient-reported change in pain (TRANS-Q), while correlations with change-scores on the other instruments were <0.35. The MIC was 2.4 DAP points. CONCLUSIONS: The DAP possesses divergent validity compared to other instruments for knee OA, supporting the potential for this new way of assessing pain directly during activity. Importantly, the DAP change-scores correspond to patient-reported changes in pain, showing responsiveness. A change of 2.4 or more can be interpreted as clinically relevant. The DAP is a promising alternative to using ‘pain on walking’ as a clinical trial inclusion criterion/outcome

Intra-Articular Corticosteroids in Addition to Exercise for Reducing Pain Sensitivity in Knee Osteoarthritis:Exploratory Outcome from a Randomized Controlled Trial

OBJECTIVE:To assess the effects of one intra-articular corticosteroid injection two weeks prior to an exercise-based intervention program for reducing pain sensitivity in patients with knee osteoarthritis (OA). DESIGN:Randomized, masked, parallel, placebo-controlled trial involving 100 participants with clinical and radiographic knee OA that were randomized to one intra-articular injection on the knee with either 1 ml of 40 mg/ml methylprednisolone (corticosteroid) dissolved in 4 ml lidocaine (10 mg/ml) or 1 ml isotonic saline (placebo) mixed with 4 ml lidocaine (10 mg/ml). Two weeks after the injections all participants undertook a 12-week supervised exercise program. Main outcomes were changes from baseline in pressure-pain sensitivity (pressure-pain threshold [PPT] and temporal summation [TS]) assessed using cuff pressure algometry on the calf. These were exploratory outcomes from a randomized controlled trial. RESULTS:A total of 100 patients were randomized to receive either corticosteroid (n = 50) or placebo (n = 50); 45 and 44, respectively, completed the trial. Four participants had missing values for PPT and one for TS at baseline; thus modified intention-to-treat populations were analyzed. The mean group difference in changes from baseline at week 14 was 0.6 kPa (95% CI: -1.7 to 2.8; P = 0.626) for PPT and 384 mm×sec (95% CI: -2980 to 3750; P = 0.821) for TS. CONCLUSIONS:These results suggest that adding intra-articular corticosteroid injection 2 weeks prior to an exercise program does not provide additional benefits compared to placebo in reducing pain sensitivity in patients with knee OA. TRIAL REGISTRATION:EU clinical trials (EudraCT): 2012-002607-18

The concept of physical limitations in knee osteoarthritis: as viewed by patients and health professionals

Objective: To comprehensively identify components of the physical limitation concept in knee osteoarthritis (OA) and to rate the clinical importance of these using perspectives of both patients and health professionals.Design: Concept mapping, a structured group process, was used to identify and organize data in focus groups (patients) and via a global web-based survey (professionals). Ideas were elicited through a nominal group technique and then organized using multidimensional scaling, cluster analysis, participant validation, rating of clinical importance, and thematic analyses to generate a conceptual model of physical limitations in knee OA. Results: Fifteen Danish patients and 200 international professionals contributed to generating the conceptual model. Five clusters emerged: &lsquo;Limitations/physical deficits&rsquo;; &lsquo;Everyday hurdles&rsquo;; &lsquo;You&rsquo;re not the person you used to be&rsquo;; &lsquo;Need to adjust way of living&rsquo;; and &lsquo;External limitations,&rsquo; each with sub-clusters. Patients generally found their limitations more important than the professionals did. Conclusion: Patients and professionals agreed largely on the physical limitation concept in knee OA. Some limitations of high importance to patients were lower rated by the professionals, highlighting the importance of including patients when conceptualizing patient outcomes. These data offer new knowledge to guide selection of clinically relevant outcomes and development of outcome measures in knee OA