Patient-assessed health instruments for the knee: a structured review

Objectives. To identify patient-assessed health instruments specific to the knee and review evidence for reliability, validity and responsiveness. Methods. Instruments were identified through systematic searches of the literature. Information relating to instrument content, patient population, reliability, validity and responsiveness was extracted from published papers. Results. The 16 instruments that met the inclusion criteria varied in length from 4 to 42 items. The majority form a single index; six produce a profile of scores. Eight have been evaluated in patients with a variety of knee problems. All instruments have satisfactory internal or test-retest reliability. However, there is limited empirical support for the health domains of six instruments. Patients informed the development of items within just five instruments. Few authors gave explicit consideration to the size of expected relationships in tests of construct validity. Eleven instruments have evidence for responsiveness to changes in health. The minimally important difference was not determined for any of the instruments. Conclusions. In the absence of comparative evidence, the large number of patient-assessed instruments for knee problems makes instrument selection difficult. The Knee Injury and Osteoarthritis Outcome Score (KOOS), Knee Pain Scale and Oxford Knee Score have good evidence for reliability, content validity and construct validity. The KOOS and Oxford instruments also have evidence for responsiveness. The instruments have not been evaluated for all knee problems, and instrument appropriateness, including content relevance, must be assessed before application. The comparative evaluation of instruments is recommended.