The Knee injury and Osteoarthritis Outcome Score (KOOS) for lateral tibial plateau fractures- relevance, reliability and responsiveness.

Background: This study aimed to evaluate the patient-reported relevance, test-retest reliability, and responsiveness for each of the five KOOS subscales in patients with lateral tibial plateau fractures.

Methods: Adult patients with surgically treated lateral tibial plateau fractures (AO 41B) were included. The primary outcome measure was the KOOS subscales: Pain, Symptoms, Activity of Daily Living (ADL), Sport and Recreational Activities (Sport/rec), and kne-related Quality of Life (QOL). The KOOS was repeated at 14 and 15 days, six weeks, and 6 and 12 months. Content validity was partly evaluated by patients ranking the relevance of all the items in the KOOS, test-retest reliability by an interclass correlation coefficient, and responsiveness by effect size and based on 3 pre-defined hypotheses related the the global rating of change.

Results: Forty-one patients with a mean age of 54.8 years (ranging from 21 to 81 years) were included. The results showed an acceptable relevance of all the KOOS subscales. The test-retest reliability was moderate to high for all five subscales, with an interclass-correlation coefficient ranging from 0.6 to 0.9. At the 6- and 12-month follow-ups, the responsiveness showed large effect sizes for all the KOOS subscales, ranging from 0.9 to 2.1. Moderate to high correlations (r ≥ 0.4)was observed for the predefine hypotheses.

Conclusion: The KOOS questionnaire showed acceptable relevance, high test-retest reliability and acceptable responsivness within one year following a lateral tibial plateau fracture. More research is needed for further validation of psychometric properties of KOOS for patients with lateral tibial plateau fractures.