Are visual assessments of the single-leg squat valid to be used in clinical practice? A systematic review of measurement properties based on the COSMIN guideline.

OBJECTIVE:Evaluate the discriminative and convergent validity of visual scales for the assessment of movement quality in the single-leg squat. METHODS:Searches performed in CINAHL, Cochrane, Embase, PubMed, SPORTDiscus and Web of Science databases. Studies evaluating discriminative and convergent validity of movement quality visual assessments in single-leg squats were included. The COSMIN risk of bias checklist was used to assess the risk of bias, and certainty of evidence was assessed by the GRADE modified version. RESULTS:Ten studies evaluating three different methods of visual assessment of the single-leg squat (Crossley scale; Whatman score and Medial knee displacement) were included. Very low certainty evidence suggests that the Crossley scale had sufficient discriminative validity for patient-centred outcomes. Very low to moderate certainty evidence suggests that the three visual methods of assessment of the single-leg squat had insufficient discriminative validity for surrogate outcomes and groups. None of the three methods had the convergent validity assessed. CONCLUSION:The Crossley scale exhibited sufficient discriminative validity for patient-centred outcomes, although the evidence supporting this conclusion is of very low certainty. Visual scales for the assessment of the single-leg squat movement quality should be used with caution in clinical practice as most methods had insufficient discriminative validity and no reports of convergent validity.