The Reliability and Meaningfulness of the Anterior Knee Pain and Lower Extremity Functional Scales in Patellofemoralpain Syndrome

Two very common scales used in the assessment of patellofemoral pain syndrome are the anterior knee pain scale and the lower extremity functional scale. There is only limited evidence regarding how specifically reliable and meaningful these scales are when assessing the syndrome. The purpose of this study was to assess which questions in both scales are suitable for patellofemoral pain syndrome patients. 20 patients with patellofemoral pain were recruited from the physiotherapy waiting list of the local hospital and asked to complete the anterior knee pain scale and the lower extremity functional scale on two occasions at least one week apart. A general test-retest reliability of the scales was measured in addition with test-retest and internal consistency of each single question. Finally, the questions marked as ‘no problem’ in both sessions were also measured. The total scores of the two scales were found to be highly reliable. However, the anterior knee pain scale revealed five questions with moderate test retest reliability, two questions with less internal consistency whilst it included three less meaningful questions. The lower extremity functional scale showed four questions with moderate test retest reliability, one question with less internal consistency and six meaningless questions. This study agrees with previous research stating that there are questions in both scales that can be considered meaningless and less reliable and should probably be excluded or replaced with other questions. The study provides useful information for the development of a more appropriate patellofemoral pain syndrome scale or a modified anterior knee pain scale and lower extremity functional scale for patellofemoral pain syndrome use only.