Research question: There is currently no validated measurement instrument for research and clinical use that can be used in the early rehabilitation process after surgical treatment of lower extremity injuries in competitive and amateur athletes. Therefore, a new questionnaire (Lower Extremity Early Rehabilitation Score-13, LERAS-13) was developed and validated to measure return to work, sport and everyday activities in the early and mid-rehabilitation period. Methodology: The questionnaire consists of questions on the work situation and workloads, return to work and sport as well as 13 items with subjective self-assessments on activities of daily living, from which a total score is calculated. It contains elements from validated knee joint-related function scores and was supplemented with relevant activities from daily life (e.g. crawling, operating foot pedals, walking on rough terrain, pushing or pulling). The questionnaire was developed using the Delphi method and validated according to the COSMIN guideline in German as part of a randomised controlled, single-blind clinical trial (DRKS00021739). At the time of analysis, data from 92 patients (m:w 58:41, age 18-63 years) after rupture and replacement of the anterior cruciate ligament were available up to 6 weeks post surgery. The correlations of the LERAS-13 with validated standard questionnaires from the field (sIKDC, ACL-RSI) as well as the internal consistency (Cronbach's alpha) and the test-retest reliability were calculated. Results: The measurement instrument showed very good internal consistency (between 0.87-0.97) and good test-retest reliability (between 0.75-0.92) for all measurement time points. The LERAS-13 correlated with knee joint function (sIKDC, r = 0.5-0.7, each p < 0.001) three and six weeks post surgery. In contrast, there were only minor non-significant correlations with an assessment of the psychological aspects of rehabilitation (ACL-RSI), which demonstrates the high validity of the instrument. Conclusions: This new, easy-to-use, digital questionnaire is a valid instrument for recording patient-relevant endpoints, in particular return to daily life and work after surgical treatment of lower limb injuries. It closes the gap in existing measurement instruments and enables standardised quantification of individual rehabilitation progress in the early rehabilitation phase for the first time. This means that treatment strategies can be individually evaluated at an early stage and adapted if necessary.

The authors have declared no competing interest.

DRKS: 00021739

This study was funded by OPED GmbH

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Ethics Committee: The Ethics Committee of Charite, Universitaetsmedizin Berlin, Campus Charite Mitte, Chariteplatz 1, 10117 Berlin The ethics vote (german language) will be sent upon request.

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