Visual assessment of movement quality in the single leg squat test: a review and meta-analysis of inter-rater and intrarater reliability

Single leg squat (SLS) is a common tool used in clinical examination to set and evaluate rehabilitation goals, but also to assess lower extremity function in active people. OBJECTIVES: To conduct a review and meta-analysis on the inter-rater and intrarater reliability of the SLS, including the lateral step-down (LSD) and forward step-down (FSD) tests. DESIGN: Review with meta-analysis. DATA SOURCES: CINAHL, Cochrane Library, Embase, Medline (OVID) and Web of Science was searched up until December 2018. ELIGIBILITY CRITERIA: Studies were eligible for inclusion if they were methodological studies which assessed the inter-rater and/or intrarater reliability of the SLS, FSD and LSD through observation of movement quality. RESULTS: Thirty-one studies were included. The reliability varied largely between studies (inter-rater: kappa/intraclass correlation coefficients (ICC) = 0.00–0.95; intrarater: kappa/ICC = 0.13–1.00), but most of the studies reached ‘moderate’ measures of agreement. The pooled results of ICC/kappa showed a ‘moderate’ agreement for inter-rater reliability, 0.58 (95% CI 0.50 to 0.65), and a ‘substantial’ agreement for intrarater reliability, 0.68 (95% CI 0.60 to 0.74). Subgroup analyses showed a higher pooled agreement for inter-rater reliability of ≤3-point rating scales while no difference was found for different numbers of segmental assessments. CONCLUSION: Our findings indicate that the SLS test including the FSD and LSD tests can be suitable for clinical use regardless of number of observed segments and particularly with a ≤3-point rating scale. Since most of the included studies were affected with some form of methodological bias, our findings must be interpreted with caution. PROSPERO registration number CRD42018077822.