Test-retest Reliability and Correlates of 6-minute Walk Test in Patients with Primary Osteoarthritis of Knees

Background: In the assessment of primary osteoarthritis (OA) of knees several clinical tool including 6 minutes walk test (6 MWT) are used. The objective of this study was to to analyze the test-retest reliability of 6 MWT and its correlation with various parameters.Methods: Eighty patients (age, 56-79 years) with OA of knees met the inclusion criteria. Demographic and clinical characteristics including radiological severity of OA (by X-ray K/L grading) were recorded. Patients filled in the knee injury and osteoarthritis outcome score (KOOS) questionnaire. All patients performed 6 MWT twice with at least 48 h gap in-between.Results: Test–retest reliability of 6 MWT in primary OA knee patients was excellent with ICC 0.991 (95% confidence interval was 0.986–0.994). 6 MWT had a weak correlation with KOOS-symptom and KOOS-activities of daily living (rho = 0.397 and 0.364 respectively), a strong correlation with KOOS-pain and KOOS-sports (rho = 0.605 and 0.521 respectively), and a very strong correlation with KOOS-quality of life (rho = 0.758). It had a weak correlation with age and height (r = 0.497 and 0.302), a strong correlation with VAS, weight, and BMI (rho = −0.655, r = −0.510, and − 0.691, respectively), and a very strong correlation with disease severity (rho = −0. 849).Conclusion: 6 MWT was a reliable test and positively correlated with all KOOS subscales and negatively correlated with other parameters except height in primary OA knee.