Four Outcome Measures for Patellofemoral Joint Problems: Part 2. Reliability and clinical sensitivity

Abstract

Background and Purpose This work represents part of a PhD project investigating outcome measures for patellofemoral joint problems – critical angle and angular velocity as measured by video analysis of an eccentric step test, a treadmill test and a Modified Functional Index Questionnaire (MFIQ). This paper presents the results of a clinical trial that investigated the issues of reliability, clinical sensitivity and agreement between the outcome measures. Methods A controlled repeated measures study was carried out in the physiotherapy department at Burnley General Hospital, where 88 patients were considered for inclusion. The patients were assessed using the four outcome measures at four separate visits. The first two assessments took place before treatment began (control period). Assessment 3 was on the day of discharge, and assessment 4 took place at three-month follow-up. Results Reliability was assessed during the pre-treatment control period using paired t-tests and no statistically significant changes in mean scores occurred. Clinical sensitivity was assessed by comparing the change in mean scores for each of the outcome measures to the 95% CI obtained during the pre-treatment control period. Only the MFIQ showed a mean change in score (13 points) that was greater than the 95% CI obtained during the control period (11.2 points). The level of agreement was assessed using a linear regression model with MFIQ as the primary response variable. Critical angle was not predictive of MFIQ scores. Angular velocity and the treadmill test together accounted for18% of the predicted change in MFIQ score. Conclusion Critical angle does not appear to be a useful outcome measure. Angular velocity and the treadmill test have potential but require further investigation. The MFIQ is the most useful with a change of 10 points probably being clinically significant. It is recommended that this questionnaire be used routinely by physiotherapists to measure outcome in patellofemoral patients. This work represents part of a PhD project investigating outcome measures for patellofemoral joint problems – critical angle and angular velocity as measured by video analysis of an eccentric step test, a treadmill test and a Modified Functional Index Questionnaire (MFIQ). This paper presents the results of a clinical trial that investigated the issues of reliability, clinical sensitivity and agreement between the outcome measures. A controlled repeated measures study was carried out in the physiotherapy department at Burnley General Hospital, where 88 patients were considered for inclusion. The patients were assessed using the four outcome measures at four separate visits. The first two assessments took place before treatment began (control period). Assessment 3 was on the day of discharge, and assessment 4 took place at three-month follow-up. Reliability was assessed during the pre-treatment control period using paired t-tests and no statistically significant changes in mean scores occurred. Clinical sensitivity was assessed by comparing the change in mean scores for each of the outcome measures to the 95% CI obtained during the pre-treatment control period. Only the MFIQ showed a mean change in score (13 points) that was greater than the 95% CI obtained during the control period (11.2 points). The level of agreement was assessed using a linear regression model with MFIQ as the primary response variable. Critical angle was not predictive of MFIQ scores. Angular velocity and the treadmill test together accounted for18% of the predicted change in MFIQ score. Critical angle does not appear to be a useful outcome measure. Angular velocity and the treadmill test have potential but require further investigation. The MFIQ is the most useful with a change of 10 points probably being clinically significant. It is recommended that this questionnaire be used routinely by physiotherapists to measure outcome in patellofemoral patients.