Background: With the increasing prevalence of total knee replacement (TKR) due to knee osteoarthritis, the absence of patient-reported outcome measures in Slovenia must be addressed.
Questions/purposes: (1) We cross-culturally adapted Oxford Knee Score (OKS) and Lower Extremity Functional Scale (LEFS) questionnaires to the Slovenian-speaking community. (2) We evaluated OKS and LEFS psychometric characteristics.
Patients and methods: In the first assessment (Time 1) Slovenian versions of both questionnaires (OKS-Slo and LEFS-Slo), knee pain, timed-up to go (TUG) and sit to stand (STS) tests were completed by 123 subjects (55% females), of which 78 were patients scheduled for TKR and 45 were healthy age-matched controls. The questionnaires were assessed one week apart (Time 2) to investigate the test-retest reliability, with 121 subjects (98.4%) completing second measurements.
Results: Significant differences were observed between the two groups. Where patients had greater body mass index, they were slower in TUG, weaker in STS, had greater knee pain in both knees and scored lower on both questionnaires. Additionally, correlation analysis showed that OKS-Slo and LEFS-Slo correlated almost perfectly (correlation coefficient [CC] = .968, p < 0.001). Excellent negative correlations were observed with TUG (OKS-Slo/CC = - 0.679, p < 0.001; LEFS-Slo/CC = - 0.692, p < 0.001) and STS (OKS-Slo/CC = 0.790, p < 0.001; LEFS-Slo/CC = 0.815, p < 0.001) tests, while knee pain of affected leg correlated the most (OKS-Slo/CC = - 0.923, p < 0.001; LEFS-Slo/CC = - 0.915, p < 0.001). The Cronbach's alpha coefficient for both the OKS-Slo and LEFS-Slo ranged between 0.87 and 0.99, while the interclass correlation coefficient was excellent; i.e., 0.99. Finally, both questionnaires proved to be unidimensional measures.
Conclusion: The Slovenian version of both questionnaires is feasible, valid and reliable for use in clinical studies including the older adult population in Slovenia.
Level of evidence: Level III, Diagnostic-case-control study.
Keywords: Osteoarthritis; Physical function; Psychometric properties; Quality of life; Self-reported measures.