Validation of a new symptom outcome for knee osteoarthritis: the Ambulation Adjusted Score for Knee pain

Pain-phenotyping in osteoarthritis: Current concepts, evidence, and considerations towards a comprehensive framework for assessment and treatment

Objectives

Pain as central symptom of osteoarthritis (OA) needs to be addressed as part of successful treatment. The assessment of pain as feature of disease or outcome in clinical practice and drug development remains a challenge due to its multidimensionality and the plethora of confounders. This article aims at providing insights into our understanding of OA pain-phenotypes and suggests a framework for systematic and comprehensive assessments.

Methods

This narrative review is based on a search of current literature for various combinations of the search terms "pain-phenotype" and "knee OA" and summarizes current knowledge on OA pain-phenotypes, putting OA pain and its assessment into perspective of current research efforts.

Results

Pain is a complex phenomenon, not necessarily associated with tissue damage. Various pain-phenotypes have been described in knee OA. Among those, a phenotype with high pain levels not necessarily matching structural changes and a phenotype with low pain levels and impact are relatively consistent. Further subgroups can be differentiated based on patient reported outcome measures, assessments of comorbidities, anxiety and depression, sleep, activity and objective measures such as quantitative sensory testing.

Conclusions

The complexity of both OA as disease and pain in OA prompt the definition of a set of variables that facilitate assessments comparable across studies to maximize our understanding of pain, as central concern for the patient.

Defining and predicting radiographic knee osteoarthritis progression: a systematic review of findings from the osteoarthritis initiative

PURPOSE

The purposes of this systematic review were to (1) identify the commonly used definitions of radiographic KOA progression, (2) summarize the important associative risk factors for disease progression based on findings from the OAI study and (3) summarize findings from radiographic KOA progression prediction modeling studies regarding the characterization of progression and outcomes.

METHODS

A systematic review was performed by conducting a literature search of definitions, risk factors and predictive models for radiographic KOA progression that utilized data from the OAI database. Radiographic progression was further characterized into "accelerated KOA" and "typical progression," as defined by included studies.

RESULTS

Of 314 studies identified, 41 studies were included in the present review. Twenty-eight (28) studies analyzed risk factors associated with KOA progression, and 13 studies created or validated prediction models or risk calculators for progression. Kellgren-Lawrence (KL) grade based on radiographs was most commonly used to characterize KOA progression (50%), followed by joint space width (JSW) narrowing (32%) generally over 48 months. Risk factors with the highest odds ratios (OR) for progression included periarticular bone mineral density (OR 10.40), any knee injury within 1 year (OR 9.22) and baseline bone mineral lesions (OR 7.92). Nine prediction modeling studies utilized both clinical and structural risk factors to inform their models, and combined models outperformed purely clinical or structural models.

CONCLUSION

The cumulative evidence suggests that combinations of structural and clinical risk factors may be able to predict radiographic KOA progression, particularly in patients with accelerated progression. Clinically relevant and feasible prediction models and risk calculators may provide valuable decision-making support when caring for patients at risk of KOA progression, although standardization in modeling and variable identification does not yet exist.

Change in pain and its relation to change in activity in osteoarthritis

Objective

Trials testing promising interventions in knee osteoarthritis (OA) often fail to show pain reductions. This may be due to change in activity whereby a person's pain decreases, leading them to increase their activity levels, in turn increasing pain back to baseline levels. Using data from a trial of a beneficial treatment for knee pain, we explored whether activity changes might mask a treatment's effect on pain, by looking at whether activity levels increased with effective treatment and whether change in activity level related to change in pain.

Design

During the InRespond trial (ISRCTN55059760) participants wore an accelerometer for 7 days before and during treatments. We assessed change in pain on treatment using scores for overall knee pain and pain in a nominated pain-aggravating activity both in the last week and evaluated change in different types of activity using accelerometer data. Principal components analysis tested whether change in activity and pain outcomes were correlated and created composites combining them. We then tested whether activity, pain or the composites showed a treatment effect, and examined their responsiveness.

Results

In the 61 participants (mean age 64.5 years, 38% women, mean overall knee pain score 5.08 (0-10)), activity levels mostly decreased during the trial. Principal component analyses suggested that pain and activity did not correlate highly, loading on different components. Treatment that showed significant effects on pain did not show similar effects on either activity (e.g. the active treatment had a slightly greater reduction in total steps taken than the control treatment (difference 1942.6 steps/week, p = 0.42) nor on composites combining activity and pain. Pain outcomes were the most responsive; static loading (standing) outcomes were the most responsive activity outcome.

Conclusion

We found no evidence to support the hypothesis that activity levels increase during effective OA treatment and might account for the negligible pain effects of OA treatments.