Analysis of outcome measures for persons with patellofemoral pain: which are reliable and valid?1,

https://doi.org/10.1016/S0003-9993(03)00613-0Get rights and content

Abstract

Crossley KM, Bennell KL, Cowan SM, Green S. Analysis of outcome measures for persons with patellofemoral pain: which are reliable and valid? Arch Phys Med Rehabil 2004;85:815-22.

Objective

To examine the test-retest reliability, validity, and responsiveness of several outcome measures in the treatment of patellofemoral pain.

Design

Evaluation of the clinimetric properties of individual outcome measures for patellofemoral pain treatment, using data collected from a previously published randomized controlled trial (RCT).

Setting

General community and private practice.

Participants

The data from 71 persons enrolled in an RCT of a conservative intervention for patellofemoral pain were used to evaluate the measures’ validity and responsiveness. A subset of this cohort (n=20) was used to assess reliability.

Interventions

Not applicable.

Main outcome measures

Three 10-cm visual analog scales (VASs) for usual pain (VAS-U), worst pain (VAS-W), and pain on 6 aggravating activities (walking, running, squatting, sitting, ascending and descending stairs) (VAS-activity); the Functional Index Questionnaire (FIQ); the Anterior Knee Pain Scale (AKPS); and the global rating of change.

Results

The test-retest reliability ranged from poor (intraclass correlation coefficient [ICC]=.49) to good (ICC=.83), and the measures correlated moderately with each other (r range, .56–.72). Median change scores differed significantly between improved and unimproved persons for all measures. The effect sizes for VAS-U (.79), VAS-W (.88), and the AKPS (.98) were large, indicating greater responsiveness than the FIQ (.37) and VAS-activity (.66). Similarly, the AKPS and VAS-W were the most efficient measures for detecting a treatment effect when compared with a reference measure (VAS-U, which was assigned a value of 1). The minimal difference that patients or clinicians consider clinically important for the AKPS is 10 (out of 100) points and for the VAS it is 2cm (out of 10cm).

Conclusions

The AKPS and VAS for usual or worst pain are reliable, valid, and responsive and are therefore recommended for future clinical trials or clinical practice in assessing treatment outcome in persons with patellofemoral pain.

Section snippets

Methods

The analyses for this study were performed using the results of a randomized, double-blind, placebo-controlled trial that evaluated the efficacy of conservative treatment for patellofemoral pain.5 In that trial, 71 participants (age range, 12–40y) were recruited from among health professionals, by advertisements, and through the media in Melbourne, Australia. For all participants, outcome assessment was performed by 1 of the 2 investigators (KMC, SMC), who were blinded to group allocation. For

Results

Of the 71 participants who enrolled in the trial, 67 (33 physiotherapy, 34 placebo) completed the final assessment and were included in the analyses of the validity and responsiveness of outcome measures. Subject characteristics are described in table 1. There were 23 women and 13 men in the physiotherapy group and 23 women and 12 men in the placebo group. There were no differences in the frequency of leg dominance or side of worst pain between the 2 groups. Visual analysis of baseline data

Discussion

This study evaluated the outcome measures used in a clinical trial of treatment for patellofemoral pain. The results indicate that the VAS-U and the AKPS were the most responsive outcome measures in this patient population. The minimal clinically relevant difference required to detect a treatment effect was calculated for each measure, thus enabling recommendations for future trials. The following is a discussion of the results of the empirical testing of the outcome measures (reliability,

Conclusions

There is no criterion standard outcome measure to assess outcomes of treatment for patellofemoral pain. Therefore, clinical trials have traditionally used a combination of outcome measures designed to address the pain, disability, and functional capacity of participants with patellofemoral pain. This study investigated the reliability, validity, and responsiveness of several outcome measures. The results of these tests indicate that the VAS for usual or worst pain and AKPS are the most valid

References (30)

  • D.I. Clark et al.

    Physiotherapy for anterior knee paina randomised controlled trial

    Ann Rheum Dis

    (2000)
  • E.L. Harrison et al.

    A randomized controlled trial of physical therapy treatment programs in patellofemoral pain syndrome

    Physiother Can

    (1999)
  • F. Angst et al.

    Smallest detectable and minimal clinically important differences of rehabilitation interventions with their implications for acquired sample sizes using WOMAC and SF-36 quality of life measurement instruments in patients with osteoarthritis of the lower extremities

    Arthritis Rheum

    (2001)
  • R. Thomee

    A comprehensive treatment approach for patellofemoral pain syndrome in young women

    Phys Ther

    (1997)
  • M.G. Kowall et al.

    Patellar taping in the treatment of patellofemoral pain. A prospective randomized study

    Am J Sports Med

    (1996)
  • Cited by (527)

    View all citing articles on Scopus

    Supported by the Physiotherapy Research Foundation and Health Professional Training fellowships from the National Health and Medical Research Council (Australia) (Regkey nos. 209168, 251762).

    1

    No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s) or upon any organization with which the author(s) is/are associated.

    View full text