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Reliability and validity of the patellofemoral disability index as a measure of functional performance and subjective pain in subjects with patellofemoral pain syndrome
Physical Therapy Rehabilitation Science 2018;7:61-6
Published online June 30, 2018
© 2018 Korean Academy of Physical Therapy Rehabilitation Science.

Mastour Saeed Alshaharania , Everett Bernell Lohmanb, Khaled Bahjric, Travis Harpd, Mansoor Alamerib, Noha S. Dahere

aRehabilitation Science, School of Allied Health Professions, Loma Linda University, Loma Linda, CA, USA, bDepartment of Physical Therapy, School of Allied Health Professions, Loma Linda University, Loma Linda, CA, USA, cPharmaceutical & Administrative Science, School of Pharmacy, Loma Linda University, Loma Linda, CA, USA, dAccentCare-home Healthcare Service, Dallas, TX, USA, eAllied Health Studies, School of Allied Health Professions, Loma Linda University, Loma Linda, CA, USA
Correspondence to: Mastour Saeed Alshaharani, Rehabilitation Science, School of Allied Health Professions, Loma Linda University, Nichol Hall Room 1605, Loma Linda, CA 92350, USA, Tel: 1-216-527-4585 E-mail:
Received April 11, 2018; Revised May 2, 2018; Accepted May 4, 2018.
cc This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Objective: Patellofemoral pain syndrome (PFPS) is a condition that is characterized by patellar discomfort or pain that is aggravated during certain activities such as ascending/descending stairs. The Patellofemoral Disability Index (PDI) was developed to assess the effect of pain on functional activities in individuals with PFPS. The objectives of the current study were to determine the internal consistency, test-retest reliability, and validity of this index.
Design: Cross-sectional study.
Methods: Forty-one subjects who had PFPS with a mean age of 28.8±5.0 years and a mean body mass index of 25.6±4.7 kg/m2 participated in the study. All subjects were concurrently enrolled in a clinical trial for which they were instructed to complete hamstring-resistance exercises for 4 weeks. Over the course of the intervention, they completed both the PDI and the Oswestry Disability Index (ODI) at baseline after two weeks, and after four weeks. Pearson correlation coefficient was used to assess the criterion validity. Cronbach’s α was used to examine the internal consistency. Intraclass correlation coefficients with 95% confidence interval were computed to examine test-retest reliability.
Results: Subjects’ responses within both the PDI and the ODI yielded Pearson correlation coefficient values that were positive and highly significant (range, 0.73-0.97; p<0.001). There was a high level of internal consistency (Cronbach’s α≥0.8), with the exception of stair climbing (Cronbach’s α=0.65). Intraclass correlation ranged from 0.87 to 0.92, indicating high levels of test-re-test reliability.
Conclusions: The PDI is a valid, reliable, and feasible method of assessing pain and functional ability in patients with PFPS.
Keywords : Anterior knee pain syndrome, Oswestry Disability Index, Patellofemoral Disability Index


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